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
Merge branch 'master' of https://github.com/CleverRaven/Cataclysm-DDA into positive-z-levels
Changed t_sky to t_open_air and changed the colours on them to make them more managable.
Fixed automap issue-apparently know up and know down are bad...
Transfered 3-D Buildings and made a mod.  Players will not be able to access new z-levels unless they use the debugger.
Reverted buildings back to their orignal settings.
Change a bunch of functions to use iterators
Make error messages show properly when getting certain computer failures

Also change them to use iterators
Convert most of construction.cpp to use iterators
Convert almost all of crafting.cpp to use iterators
Change some of creature_tracker.cpp to use iterators
Change parts of defense.cpp to use iterators
Change dependency_tree.cpp to use iterators
Change disease.cpp to use iterators
Change most of editmap.cpp to use iterators
Change faction.cpp to use iterators