Adds floor painter

Adds a floor painter, which can be used to switch between most styles of floor tile currently present in floors.dmi (notable exception: SS13/derelict floor markers).
Uses the hand labeller sprite (the pipe painter uses the same sprite).

Not mapped in, not legitimately obtainable in-game with the code in this PR (admin spawning excepted).

The placed tile is adjusted based on where you stand relative to the tile, so by clicking with the "side/three corners" option on all 8 adjacent tiles, you will end up with a box as shown below:
![](http://puu.sh/aPISM/909e02cdfd.png)

Main menu
![](http://puu.sh/aPIDA/bf14d333c5.png)

'opposite corners' sub-menu
![](http://puu.sh/aPIER/afa61eaab2.png)

Names in the menu are based on the icon_state names to avoid needing the sort of switch() statement that I needed for the 'letters' sub-menu (L162).