Correction of bugs : missile's speed and support tower
Solving the areaMissile concurrent modification exception
Optimisation of tower's characteristics
Defined a new enum AttackType for the missiles
Medical tower effect now working
View - Small tower bug fixed
New class Effect to apply modifiers
View - Evolve tower => using the new range
Frost modifier now working
Prevent from applying twice the same effect to the same unit
Shield modifier now working
View  - New add tower images + % base faster
Merge branch 'thomas'

Conflicts:
	src/GameEngine/GameManager.java
	src/GameEngine/WarManager.java
Merge branch 'aurelie'

Conflicts:
	src/GameEngine/GameManager.java
Fix misplacement of AI towers