This patch changes nitpicker's session interface to use session-local
view handles instead of view capabilities. This enables the batching
of multiple view operations into one atomic update.
Now that it is possible to resize the stack of the Genode main thread, it
is not necessary anymore to create a new Genode thread as Qt main thread.
Fixes#1134.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082