AI Support Power Meta Data implemented.

Changes included:
Decision can be defined for the AI support powers, governing their targeting.
Each decision can be made up of multiple considerations.
Merge pull request #5867 from UberWaffe/AI-MetaData

Closes #2926
Closes #5830
Closes #6207
Remove unused method
Ensure that all combatants have a defined WinState at the end of the game
Fix OnObjective(Completed|Failed) not being called for secondary objectives
Make ScriptContext available in Actor- and PlayerProperty classes

Needed to return non-native types to Lua
Add OnCapture, OnAddedToWorld and OnRemovedFromWorld triggers to Lua API

This brings the new Lua API up to feature-parity with the old API in the
trigger department.
Add a number of small helper functions to Lua API
Add reinforcements functions to Lua API
Adjust gdi01 to use new functions
Replace explicit Dispose() calls with using statements in ScriptTrigger.cs