Load all files in data/json automatically.
Move construction specification to new data/json/construction.json.
Display only theoretically available constructions, and group them.
Also display the terrain a construction replaces, if any.
Allow wooden walls to be built over empty window frames.
Fix debugmsg about missing materials.
Gettext construction descriptions.
remove mapbuffer loading when starting a special game mode

in the code before that, the special map has been generated for this special game mode, but this overwrites the content of the mapbuffer with data from disk.
This lead to the situation that the map has pointers to submaps that are not stored in mapbuffer (mapbuffer was reset on load). Those activly used submaps (still referenced from map) would not be stored as mapbuffer did not know them (mapbuffer::add_submap ignores new submaps if it already knows a submap for that point)
Fix display of terrain when choosing where to construct.
Don't consider consrtuctions that wouldn't change the terrain.
Refresh display after choosing an item to use.
Merge fix to mapbuffer handling in special game modes.
Merge json loaing fix and jsonized construction recipes.

Conflicts:
	src/init.cpp