ErgDB Download - add erg2 extension and uncheck All by default

Add erg2 extension as one of admited workout formats to avoid
Scan Workouts removing all referenes to them.
Also uncheck Select All setting by default since currently
there are hundreds of workouts and downloading all of them is unlikely
what the users want to do, besides they are not that easy to remove.

src/Train/ErgDBDownloadDialog.cpp

@@ -67,7 +67,7 @@ ErgDBDownloadDialog::ErgDBDownloadDialog(Context *context) : QDialog(context->ma
 
         // selector
         QCheckBox *checkBox = new QCheckBox("", this);
-        checkBox->setChecked(true);
+        checkBox->setChecked(false);
         files->setItemWidget(add, 0, checkBox);
 
         add->setText(1, item.name);
@@ -83,7 +83,7 @@ ErgDBDownloadDialog::ErgDBDownloadDialog(Context *context) : QDialog(context->ma
     }
 
     all = new QCheckBox(tr("check/uncheck all"), this);
-    all->setChecked(true);
+    all->setChecked(false);
 
     // buttons
     QHBoxLayout *buttons = new QHBoxLayout;

src/Train/ErgFile.cpp

@@ -43,6 +43,7 @@ static bool setSupported()
     ::supported << ".gpx";
     ::supported << ".tts";
     ::supported << ".json";
+    ::supported << ".erg2";
 
     return true;
 }