Replace VFileSystemWatcher with QFileSystemWatcher.

The former has some problems runs out of file descriptors with inotify
making impossible for the Desktop Shell to be executed.
Rename directoryChanged() slot.
Pick up latest qt-accountsservice-addon changes.

We can now use the UserAccount type without problems.
Print EGL and OpenGL strings from the rendering thread.

Following Samuel Rodal advice on the mailing list the graphics information
is now printed from the graphics thread connecting the sceneGraphInitialized()
signal with Qt::DirectConnection.
Build system improvements

Close issue #17.
Stretch wallpaper image by default

Makes the wallpaper look much better.