Remove legacy subsystem code

[heinezen]

A lot of the C++ subsystems in libopenage have been rewritten using the new decoupled architecture. However, the old (now unused) code parts are still there and should be removed one by one. We should check if parts of the code are still "salvagable" for the new architecture, but most of them are probably just dead weight by now.

• Asset management (yes, there are 3 deprecated asset managers)
  • openage::AssetManager
  • openage::LegacyAssetManager
  • openage::presenter::AssetManager
• Deprecated Coordinate types (libopenage/coord)
  • CoordManager
  • Deprecated transformations between types
• Gamedata dummy classes (libopenage/gamedata)
• Old gamestate
  • Game logic (libopenage/gamestate/old)
  • Unit handling (libopenage/unit)
• Old input system (libopenage/input/legacy)
• Old GUI (libopenage/gui)
• Old renderer
  • Logic (libopenage/presenter/legacy)
  • Data classes (texure, etc.)
• Old Terrain (libopenage/terrain)