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/tasklist/tasklistplugin.cpp

@@ -35,7 +35,6 @@
 #include <projectexplorer/session.h>
 #include <projectexplorer/task.h>
 #include <projectexplorer/taskhub.h>
-#include <utils/mimetypes/mimedatabase.h>
 
 #include <QDir>
 #include <QMessageBox>
@@ -194,8 +193,6 @@ bool TaskListPlugin::initialize(const QStringList &arguments, QString *errorMess
     //: Category under which tasklist tasks are listed in Issues view
     TaskHub::addCategory(Constants::TASKLISTTASK_ID, tr("My Tasks"));
 
-    MimeDatabase::addMimeTypes(QLatin1String(":tasklist/TaskList.mimetypes.xml"));
-
     m_fileFactory = new IDocumentFactory;
     m_fileFactory->addMimeType(QLatin1String("text/x-tasklist"));
     m_fileFactory->setOpener([this](const QString &fileName) {