Add httpserver to contrib

.. see http://stefanfrings.de/qtwebapp/index-en.html

.. this is a lightweight web server to allow GC to
   provide webservices.

.. we will be providing web services on localhost to
   enable R integration.

.. we will use web services to standardise the
   interface to provide something we can use in R
   but also anything else at a later date.

.. gcconfig.pri contains $$HTPATH that points to
   the location of the code, if it is not set then
   the web server is not compiled in.

httpserver/staticfilecontroller.cpp

@@ -0,0 +1,136 @@
+/**
+  @file
+  @author Stefan Frings
+*/
+
+#include "staticfilecontroller.h"
+#include <QFileInfo>
+#include <QDir>
+#include <QDateTime>
+
+StaticFileController::StaticFileController(QSettings* settings, QObject* parent)
+    :HttpRequestHandler(parent)
+{
+    maxAge=settings->value("maxAge","60000").toInt();
+    encoding=settings->value("encoding","UTF-8").toString();
+    docroot=settings->value("path",".").toString();
+    if(!(docroot.startsWith(":/") || docroot.startsWith("qrc://")))
+    {
+        // Convert relative path to absolute, based on the directory of the config file.
+        #ifdef Q_OS_WIN32
+            if (QDir::isRelativePath(docroot) && settings->format()!=QSettings::NativeFormat)
+        #else
+            if (QDir::isRelativePath(docroot))
+        #endif
+        {
+            QFileInfo configFile(settings->fileName());
+            docroot=QFileInfo(configFile.absolutePath(),docroot).absoluteFilePath();
+        }
+    }
+    qDebug("StaticFileController: docroot=%s, encoding=%s, maxAge=%i",qPrintable(docroot),qPrintable(encoding),maxAge);
+    maxCachedFileSize=settings->value("maxCachedFileSize","65536").toInt();
+    cache.setMaxCost(settings->value("cacheSize","1000000").toInt());
+    cacheTimeout=settings->value("cacheTime","60000").toInt();
+    qDebug("StaticFileController: cache timeout=%i, size=%i",cacheTimeout,cache.maxCost());
+}
+
+
+void StaticFileController::service(HttpRequest& request, HttpResponse& response) {
+    QByteArray path=request.getPath();
+    // Check if we have the file in cache
+    qint64 now=QDateTime::currentMSecsSinceEpoch();
+    mutex.lock();
+    CacheEntry* entry=cache.object(path);
+    if (entry && (cacheTimeout==0 || entry->created>now-cacheTimeout)) {
+        QByteArray document=entry->document; //copy the cached document, because other threads may destroy the cached entry immediately after mutex unlock.
+        QByteArray filename=entry->filename;
+        mutex.unlock();
+        qDebug("StaticFileController: Cache hit for %s",path.data());
+        setContentType(filename,response);
+        response.setHeader("Cache-Control","max-age="+QByteArray::number(maxAge/1000));
+        response.write(document);
+    }
+    else {
+        mutex.unlock();
+        // The file is not in cache.
+        qDebug("StaticFileController: Cache miss for %s",path.data());
+        // Forbid access to files outside the docroot directory
+        if (path.contains("/..")) {
+            qWarning("StaticFileController: detected forbidden characters in path %s",path.data());
+            response.setStatus(403,"forbidden");
+            response.write("403 forbidden",true);
+            return;
+        }
+        // If the filename is a directory, append index.html.
+        if (QFileInfo(docroot+path).isDir()) {
+            path+="/index.html";
+        }
+        // Try to open the file
+        QFile file(docroot+path);
+        qDebug("StaticFileController: Open file %s",qPrintable(file.fileName()));
+        if (file.open(QIODevice::ReadOnly)) {
+            setContentType(path,response);
+            response.setHeader("Cache-Control","max-age="+QByteArray::number(maxAge/1000));
+            if (file.size()<=maxCachedFileSize) {
+                // Return the file content and store it also in the cache
+                entry=new CacheEntry();
+                while (!file.atEnd() && !file.error()) {
+                    QByteArray buffer=file.read(65536);
+                    response.write(buffer);
+                    entry->document.append(buffer);
+                }
+                entry->created=now;
+                entry->filename=path;
+                mutex.lock();
+                cache.insert(request.getPath(),entry,entry->document.size());
+                mutex.unlock();
+            }
+            else {
+                // Return the file content, do not store in cache
+                while (!file.atEnd() && !file.error()) {
+                    response.write(file.read(65536));
+                }
+            }
+            file.close();
+        }
+        else {
+            if (file.exists()) {
+                qWarning("StaticFileController: Cannot open existing file %s for reading",qPrintable(file.fileName()));
+                response.setStatus(403,"forbidden");
+                response.write("403 forbidden",true);
+            }
+            else {
+                response.setStatus(404,"not found");
+                response.write("404 not found",true);
+            }
+        }
+    }
+}
+
+void StaticFileController::setContentType(QString fileName, HttpResponse& response) const {
+    if (fileName.endsWith(".png")) {
+        response.setHeader("Content-Type", "image/png");
+    }
+    else if (fileName.endsWith(".jpg")) {
+        response.setHeader("Content-Type", "image/jpeg");
+    }
+    else if (fileName.endsWith(".gif")) {
+        response.setHeader("Content-Type", "image/gif");
+    }
+    else if (fileName.endsWith(".pdf")) {
+        response.setHeader("Content-Type", "application/pdf");
+    }
+    else if (fileName.endsWith(".txt")) {
+        response.setHeader("Content-Type", qPrintable("text/plain; charset="+encoding));
+    }
+    else if (fileName.endsWith(".html") || fileName.endsWith(".htm")) {
+        response.setHeader("Content-Type", qPrintable("text/html; charset="+encoding));
+    }
+    else if (fileName.endsWith(".css")) {
+        response.setHeader("Content-Type", "text/css");
+    }
+    else if (fileName.endsWith(".js")) {
+        response.setHeader("Content-Type", "text/javascript");
+    }
+    // Todo: add all of your content types
+}