Replace Projectile class by Ammunition
Added Interface IControlable to PlayerShip
Reworked Weapon system

Added slots to ships to put usable items in them. Weapons are usables.
When the player hits "fire", the selected slots will trigger.
Globals now calculate rectangle areas.

Previously, it was EventHorizon class job.
Adapted Mobile to decentralized architecture.
Renamed Resources folder to Objects

The objects will not be loaded from Resources anymore.
Added UnityExtended library
Removed Gun class

Weapon is the only weapon base class
Renamed WeaponElement

==> WeaponPart

WeaponPart is the class for parts of weapons. A Weapon can be composed
of many WeaponParts.
Removed Player class

Its functionality has been dispatched to other classes. IControlable
interface for player input, EventHorizon class for instantiation of
player ship and Gameplay data.
minor changes