Kept cleaning, the game modes as fully used as is now.

- Kept removing class members referencing singletons, (it's a bad practice anyway)
  permitting to keep removing dead code along the way.
- Moved ASWrapper as a component of the mode manager
- Merge *Context classes into their respective *Mode classes
  The context class were only worth it for two rendering functions
   that had to move the *Mode classes anyway.
  The rest of those was useless referencing of singletons
  and dead members.
- Init the RenderManager only once
  (will later permit to switch the app mode without an Ogre exception).
- Successfully move the map loading part
  out the renderManager to the respective Mode classes.