Add Game basis, ECS, Documentation, proper the project namespaces

[BlowaXD]

This merge request fix the issue #4

Additions :

• IMap
• IMapLayer
• IEntity
• IEntityComponent
• IPortal

[AntoineCrb]

Instead of using int we can use short or ushort for the Height/Width, GetEntitiesInRange(int x, int y) here we also need the range as argument. But otherwise it seems good to me :)

[BlowaXD]

I missed two things :

• MapManager (Instanciate Maps from its data..)
• IMapService (to load maps datas from somewhere...)