-- time sync: Couple virtual time to wall clock

Subject

Introduce wall clock coupling of virtual time. Accessible via participant configuration:

Experimental:
  TimeSynchronization:
    AnimationFactor: 1.0

Added a WallClockCoupling thread similar to the WatchDog thread that manages the time advances when due
Prevent sending NextSimTask at other places than the WallClockCoupling thread if the coupling is active
Improved performance for mixed system w/ wo/ time synchronization by not sending NextSimTask message to participants that don't use a TimeSyncService:
- The timeSyncService is created by default with a lifecycle service, although it might be unused
- Now, controllers can be created internally without performing the message subscriptions (preventing RegisterSilKitService)
- For the TimeSyncService, the subscriptions are then performed when the user calls CreateTimeSyncService

Review code changes
Review changes to docs in configuration.rst and experimental-configuration.rst
Try with any demo: Comment out sleeps in SimStepHandler, use adapted participant config with e.g.

Experimental:
  TimeSynchronization:
    AnimationFactor: 100.0