Merge pull request #4 from mike96/master

Merge day
Added new assets
Fixed playlist crash
Added Vector2::Angle
Added Object base-class for future game entities
Fixed joystick
Implemented Player from Object
Linked joystick to Player movement
Fixed Vector2::Rotate and Vector2::Angle
Added float-point multi-layer support for SpriteBatcher (Note: Sprite have default layer 0 and TextureMappedFont have default layer 1000)
Fixed "game entities over HUD" bug
Improved source tree for "jni/Graphics/.."
Added Camera2D (includes support for Object linking and also fully support for current world entities)
Added spring system (smooth follow of linked object)
Added generic Animation and AnimationPlayer class
Fixed compiler warnings
Fixed Sprite texture coordinates
Fixed asset
Added new asset (animated explosion)
Added AnimatedSprite