[Suggestion] Rename and add alias for `apoli:entity_set` related powers/actions/conditions for clarity.

[JustCyra]

As is right now I was a bit confused when I first saw "Set Size" (apoli:set_size Entity Condition) and was mislead thinking about power holder size instead of an entity set. This would just make it more understanding what it actually is as there is no need to shorten it down to "set" instead of "entity_set", the confusion is bigger then the benefit of not writing a single additional word.

Example on how it could change:
add_to_set -> add_to_entity_set
remove_from_set -> remove_from_entity_set
action_on_set -> action_on_entity_set
in_set -> in_entity_set
set_size -> entity_set_size