[WIP] [CR] simple fullscreen mode

simple fullscreen view, good for small view dimensions or tiles (tiles not tested). 

TAB toggles it on and off. 

http://i.imgur.com/ICA2D5r.png -> http://i.imgur.com/O1MB849.png

functions that rely on the sidebar should be wrapped with temp_exit_fullscreen() and reenter_fullscreen() which exit and reenter the mode if it's active. Currently I've only done it for the item view (shift-v). 

bugs: probably many. I noticed that explosions were improperly offset for one.