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/imageviewer/imageviewerplugin.cpp

@@ -39,7 +39,6 @@
 #include <coreplugin/editormanager/editormanager.h>
 #include <coreplugin/id.h>
 #include <extensionsystem/pluginmanager.h>
-#include <utils/mimetypes/mimedatabase.h>
 
 namespace ImageViewer {
 namespace Internal {
@@ -51,8 +50,6 @@ bool ImageViewerPlugin::initialize(const QStringList &arguments, QString *errorM
     Q_UNUSED(arguments)
     Q_UNUSED(errorMessage)
 
-    Utils::MimeDatabase::addMimeTypes(QLatin1String(":/imageviewer/ImageViewer.mimetypes.xml"));
-
     m_factory = new ImageViewerFactory(this);
     addAutoReleasedObject(m_factory);
     return true;