Move mimetype definitions to plugin specs

- Avoids the hassle of QRC files and manually registering mime types
- Avoids performance regressions because of mime types that are
  registered after mime database has been used
- Makes it technically possible to detect that a disabled plugin could
  handle a mime type if it was enabled

Change-Id: I373008b1b56e9c6b4853055f20b3eeb112a6eff9
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/genericprojectmanager/genericprojectplugin.cpp

@@ -44,7 +44,6 @@
 
 #include <utils/algorithm.h>
 #include <utils/fileutils.h>
-#include <utils/mimetypes/mimedatabase.h>
 
 #include <QtPlugin>
 #include <QDebug>
@@ -58,7 +57,6 @@ namespace Internal {
 bool GenericProjectPlugin::initialize(const QStringList &, QString *errorMessage)
 {
     Q_UNUSED(errorMessage)
-    Utils::MimeDatabase::addMimeTypes(":genericproject/GenericProjectManager.mimetypes.xml");
 
     addAutoReleasedObject(new Manager);
     addAutoReleasedObject(new ProjectFilesFactory);