Improvement of Skill Memory and Skill Memory GUI

Together with @peller, we improved the skill memory and skill memory GUI. This MR ...

1. Adds various skills for testing, especially RandomChaining for extensive stress testing (when started multiple times)
2. Fixes various segmentation faults and deadlocks for the skill memory.
3. Adds 5 or 10 second timeouts for ice calls in the ARMARX skill memory gui, so it doesn't freeze.

Known open issue:

1. Skill memory still deadlocks in certain corner case during skill abortion. But this probably only happens very rarely. Reproduce by requesting execution of skill "InstantKill" and directly calling "Stop all executions".