Fluxio/dev skill timeout

See merge request !461

fluxio/dev Pointer Shenanigans

See merge request !459

when a skill is terminated (due to abort or timeout), the remaining subskills will be aborted. We now wait for a last status update before exiting the main loop and stopping the status polling thread.

changes:
 - updated fluxio skill struct and to/from ice conversion
 - implemented timeout logic in composite executor
 - get correct timeout value when converting native skill to a fluxio skill

changes:
- executions are stored as unique pointers
- replaced usage of raw pointers with smart pointers
- added mutex and locks for composit and merger executor

does compile but not tested

steps where taken:
* nodes as unique ptr
* skill no copy constr.
* skill returns as observer ptr

Fluxio/dev delete skill method

See merge request !454