* training: tests on multithreading integrated.
* training: implemented multi thread driven by the main thread.
* Ely: first attempt to integrate multithread.
* ELy: updated tinyxml2.
Merge branch 'master' into multithread
* training: modified threads conditions.
* Ely: first attempt of multithread implementation: should use mutex to
change variables.
* Ely: multithread first attempt completed. It hangs when closing.
* Ely: first implementation of multithrading based on condition
variables completed. 

* It seems to work. TODO perform more tests and then merge into master
branch.
* Ely: added generic constraint to picker. To be chosen at creation
time.
* Ely: Driver: added controls to pitch up/down.
* ely: added driver control to camera together with picker (disabling
mouse control)
* Ely: Picker: now the picked body follows the camera movements.
* Ely: NavMesh & related: updated to librecastnavigation 1.1.
* Ely: NavMesh & related: seem not working in multi-threading mode.
* Ely: NavMesh & related: now in multi-threading mode adding crowd agent
seems to work, but dynamic debug drawing not (i think it should be put
in a task in the "default" taskchain with a sort value after the
firetask one). 
* Ely: CHECK if there are other debug drawings somewhere.
* Ely: now "multithreded rendered pipeline" is enabled by default only
when ELY_THREAD are disabled. Even in this case it seems to go in
deadlock. So it could be needed to disable it any way.
* Ely: added physics Ghost component. Yo be completed.
* Ely: Ghost component: started implementation.
* Ely: tinyxml2: update.
* Ely: added "Common" family and "Default" component.
* Ely:TODO: refactoring sending events by some components.
* Ely: corrected bugs about actual event sending behavior by CrowdAgent,
SteerVehicle, CharacterController, Vehicle components. TODO:
implementation of discrete sending mode besides the actual continuous
one.
* Ely: tinyxml2: update.