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.h

@@ -0,0 +1,87 @@
+/**
+  @file
+  @author Stefan Frings
+*/
+
+#ifndef STATICFILECONTROLLER_H
+#define STATICFILECONTROLLER_H
+
+#include <QCache>
+#include <QMutex>
+#include "httpglobal.h"
+#include "httprequest.h"
+#include "httpresponse.h"
+#include "httprequesthandler.h"
+
+/**
+  Delivers static files. It is usually called by the applications main request handler when
+  the caller request a path that is mapped to static files.
+  <p>
+  The following settings are required in the config file:
+  <code><pre>
+  path=../docroot
+  encoding=UTF-8
+  maxAge=60000
+  cacheTime=60000
+  cacheSize=1000000
+  maxCachedFileSize=65536
+  </pre></code>
+  The path is relative to the directory of the config file. In case of windows, if the
+  settings are in the registry, the path is relative to the current working directory.
+  <p>
+  The encoding is sent to the web browser in case of text and html files.
+  <p>
+  The cache improves performance of small files when loaded from a network
+  drive. Large files are not cached. Files are cached as long as possible,
+  when cacheTime=0. The maxAge value (in msec!) controls the remote browsers cache.
+  <p>
+  Do not instantiate this class in each request, because this would make the file cache
+  useless. Better create one instance during start-up and call it when the application
+  received a related HTTP request.
+*/
+
+class DECLSPEC StaticFileController : public HttpRequestHandler  {
+    Q_OBJECT
+    Q_DISABLE_COPY(StaticFileController)
+public:
+
+    /** Constructor */
+    StaticFileController(QSettings* settings, QObject* parent = NULL);
+
+    /** Generates the response */
+    void service(HttpRequest& request, HttpResponse& response);
+
+private:
+
+    /** Encoding of text files */
+    QString encoding;
+
+    /** Root directory of documents */
+    QString docroot;
+
+    /** Maximum age of files in the browser cache */
+    int maxAge;
+
+    struct CacheEntry {
+        QByteArray document;
+        qint64 created;
+        QByteArray filename;
+    };
+
+    /** Timeout for each cached file */
+    int cacheTimeout;
+
+    /** Maximum size of files in cache, larger files are not cached */
+    int maxCachedFileSize;
+
+    /** Cache storage */
+    QCache<QString,CacheEntry> cache;
+
+    /** Used to synchronize cache access for threads */
+    QMutex mutex;
+
+    /** Set a content-type header in the response depending on the ending of the filename */
+    void setContentType(QString file, HttpResponse& response) const;
+};
+
+#endif // STATICFILECONTROLLER_H