Install the qml plugin that exposes kdevplatform things
Add some special treatment for kdev:// urls

This way we can use it for special pages provided by KDevelop.
Move the WelcomePage plugin to kdevplatform

After some discussion in the SDK sprint, we decided we want it to end up in
as a pinned tab. (and then decide if we like it).

A patch in Qt is still needed for it to work properly:
https://codereview.qt-project.org/#/c/92201/
First approach to a functional ProjectsDashboard
Remove debug
Add a plugin concept for the projects dashboard
Correct file names for some export headers

Some export header filenames and SUBLIME_EXPORT definition was broken by 8cc00b0e8fedeb397c4861e593ef01c1a3c69f87, this fixes it.

REVIEW: 119778
Fix and enable ProjectController Test

REVIEW: 119779
Make the document title appear correctly
Remove duplicated code
Make compile when Grantlee is found
Restore compatibility with older Qt
Renable patchreview

This was disabled by mistake
Windows compile fix

Use QThread::usleep instead of usleep from unistd.h
Remove redundant API
Make it possible to disable teh welcome page again