Implement WinRT plugin for positioning

[ChangeLog][QtPositioning][QGeoPositionInfoSource] WinRT backend added.

Change-Id: I00e7725a082aa485c3ab5afcaebd20344b48e07d
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Add snippet app to verify plugin implementation

Useful when creating a new backend to verify behavior.

Change-Id: I7a417aabad4d6dbbe494dcd384ca7af57bd78050
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Fix crash on S4 when running Satellite and Position updates concurrently

This was caused due to unsynchronized access of data between two threads.
The Java satellite updates were sent before the receiving Qt thread could
finish its regular startup. As a consequence the received updates could
not be mapped to a receiving C++ class.

This patch synchronizes the startup and setup of the two threads and
ensures that the relvant data setup on the C++ side is done before the
update thread is started.

In addition some minor debug helpers were added for future references.

Task-number: QTBUG-39082
Change-Id: I1f24ddfcef038fa000801ddb6a3ea0959370f0d3
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>