Sleeker escape shuttle, new tiles, minor map changes

Escape shuttle replaced with sleeker, nicer-looking shuttle: http://i.imgur.com/7ldNyu1.png

Added swall_floor_f5, swall_floor_f6, swall_floor_f9 and swall_floor_f10, which are smooth interior shuttle wall corners. Shuttles modified to use these instead of the blocky corners or two different overlaid turfs.

Notice board added to engineering.