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/cvs/cvs.qbs

@@ -13,7 +13,6 @@ QtcPlugin {
     files: [
         "annotationhighlighter.cpp",
         "annotationhighlighter.h",
-        "cvs.qrc",
         "cvsclient.cpp",
         "cvsclient.h",
         "cvscontrol.cpp",