Window manager

The window manager provides a nitpicker session interface. In contrast
to the nitpicker server, which leaves the view layout up to the client,
the window manager organizes the views on screen according to a policy
provided by a window layouter. Furthermore, it equips views with window
decorations as provided by a window decorator. Both layouter and
decorator are independent programs.
qt5: change mirror to HU Berlin
qt5: use window manager
qt5: Adapt qpluginwidget new nitpicker/loader

The QPluginWidget used to be a QNitpickerViewWidget but the new loader
interface does no longer hand out a view capability. So we need to
decouple both classes. This patch moves the view-geometry calculation to
a separate class to make it easier reusable, in particular for the
QPluginWidget.
qt5: Adaptation to nitpicker pointer change
Adapt run scripts to nitpicker config changes
nit_fb: use server API, make resizeable

This patch reimplements the nit_fb server using the server API and
thereby enables the dynamic resizing the of the framebuffer.

Note that the new implementation does not feature the ability to perform
a periodic refresh via the 'refresh_rate' configuration argument. This
feature was removed because the refresh policy can (and should) always
be implemented on the client side.
wm.run: temporary test for resize protocol
nitpicker: reduce artifacts during mode change