Positive Z-levels(WIP)

Since I want to add a second floor to the Rivtech facility, I need to get positive Z-levels working, since a lot of the base is already there.

After diving into the code(including that huge if statement in mapgen.cpp), I *think*, I know what needs to be done to get it working.
Merge branch 'master' of https://github.com/CleverRaven/Cataclysm-DDA into positive-z-levels
Added sky terrain, sky overmap
Finished up, everything seems to work, as I want.
Added 3-D version of Motel
Added 3-D version of Office Tower(empty) thanks to acidia
Change trap detection dynamics.

Traps now must be searched for. Candidate search radius increased to 11 squares.

Detection is combination of perception, tiredness, stimulus, luck, distance from trap, and trap visibility.

Traps must be detected before being known and seen.

Numbers probably need to be tweaked, but in my tests this seems fun despite my earlier (and overblown) apprehension.
redundant is redundantly redundant.
Removing dead code.

Not sure if map_extra_chance was kept for reference, but it's dead Jim.
Trap search done on move.
insert some comment about juggalos, science, magnets, and magic.

Oh, and maths. Search math should actually search an area of 11.

And more comments for the why the math is the way it is in search_surroundings().
Incendiary grenade item & spawns
Explosion and incendiary field
Merge branch 'master' of https://github.com/CleverRaven/Cataclysm-DDA into positive-z-levels
Merge remote-tracking branch 'upstream/master' into its_a_trap
Turned off stashes/extras... i think.
Split recipe json

Splits the recipe.json file into small easier to browse files by
category.   No more 31000 line long recipe.json.
Passenger_flag now beeing removed from affected vehicle part
Remove my ignorant comments, turn of just "stashes" not all the extras.

After fiddling with the numbers and trying out some calculations, I kept the weighted numbers as is and if stash was chosen, it acts as if no extra is chosen and falls through. This keeps all other extras appearing at the same quantity and frequency as they would appear now.
Merge remote-tracking branch 'upstream/master' into its_a_trap
Remove errant comment.