MIME types: Introduce user extensions feature

Creates a new page in the options dialog which allows
the user to modify MIME type's globl patterns and rule-based
magic matchers.

As a side-effect of this feature our MIME database (and related
components) got some improvements.

Reviewed-by: Friedemann Kleint

src/plugins/coreplugin/coreplugin.cpp

@@ -38,6 +38,7 @@
 #include "modemanager.h"
 #include "fileiconprovider.h"
 #include "designmode.h"
+#include "mimedatabase.h"
 
 #include <extensionsystem/pluginmanager.h>
 
@@ -99,6 +100,7 @@ bool CorePlugin::initialize(const QStringList &arguments, QString *errorMessage)
 
 void CorePlugin::extensionsInitialized()
 {
+    m_mainWindow->mimeDatabase()->syncUserModifiedMimeTypes();
     m_mainWindow->extensionsInitialized();
 }