refs #395, improvements for snapshot / restricted aircraft handling

* fixed isCurrentThreadCreatingThread and renamed to isCurrentThreadObjectThread (this check was never working), added 2 more thread checks
* changed remove aircraft function to return number of returned aircraft (like with the containers this allows to avoid unnecessary signals)
* removed unused function ps_recalculateRenderedAircraft() / SimulatorCommon
* using Queued airspaceAircraftSnapshot signal for binding (functor connect does not provide connection type)
* extened ASSERTs to check threads
* simulator: initial situation function with return value (success?)
* simulator: avoid unneccessary copy and provide correct rendered flag in add aircraft function

src/plugins/simulator/fscommon/simulator_fscommon.cpp

@@ -31,7 +31,7 @@ namespace BlackSimPlugin
             IRemoteAircraftProvider *renderedAircraftProvider,
             QObject *parent) :
             CSimulatorCommon(info, ownAircraftProvider, renderedAircraftProvider, parent),
-            m_fsuipc(new FsCommon::CFsuipc())
+            m_fsuipc(new CFsuipc())
         {
             // hack to init mapper
             CAircraftMapper *mapper = mapperInstance();