power specific stat modifiers

implementation of clintbellanger/flare-engine#535
clintbellanger/flare-engine#552 and clintbellanger/flare-engine#549
Replace whitespaces by tabs.
Merge minions into cutscenes_and_refactoring_and_minions

Conflicts:
	src/Avatar.cpp
	src/Enemy.cpp
	src/EnemyManager.cpp
	src/Entity.cpp
	src/Entity.h
Remove unneeded Entity::face

It was already removed in 9a2a68aa84ed90480d57c486f63c92d5f628a3dc,
but sneaked in again in the merge of the minions.