Reworked all actors and actor variable properties to use the new property system.

Resolves #406 , closes #437 , related to !350 and !325

Replaces and reworks all the actor properties and the actor property tree to use the new property system introduced in !325 . It is therefore relatively large and touches all actor classes. Saving and loading of actors will also be reworked with this MR, so compatibility code or scripts will be needed to load older actor configuration files or sessions.

The rework of the save and load logic is necessary, as the new property system allows all properties to automatically be saved when the actor is saved. This saves work on the developer side and reduces errors in the save and load logic.

Also includes some smaller code quality changes to reduce compilation and syntax warnings such as missing override statements in the reworked actors or foreach macro replacements.