Author: s20

rename shader files to be more consistent

The models were a special case so far, since those were the first shaders be added.

add setting/resetting of wall tile types

Similar to adding objects and tiles the user can now also set/reset the wall types (read: wall papers) on either side of a piece of wall.
This is slightly more complicated as in the case of tiles, as here both sides of a piece of wall have to be regarded individually.
This change had effects on the shaders, the renderer, the World class, the SelectionState, the GameState and some other crowd favourites.
What is, however, still missing though is the removal and placement of walls.

fix mutexes to protect us from threading related corruption

Once again, fewer crashes through fewer race conditions.

make tiles editable (change tile type and reset it)

Now users cannot only place and remove objects, but also tiles.

do not try to use vertex buffers that have not been created yet (due to race conditions)

Fewer crashes for everyone!

move code from the renderer to the modelpipeline where it belongs. add more comments.

That is.. that is what it does. Make the renderer just a bit smaller, bit by bit.

add support for deleting static objects

One could argue it makes sense to enable the user to also remove objects, now that they can also create them.
This also means that the renderer needs to stop making some assumptions about its data structures.
Furthermore, this refactors some part of the code a bit, for instance when resetting the current selection after deselection or a deletion happened.