Commit 2
New notable files:
src/TileDirectory.as - used for retrieving information about all tiles
lib/assets.fla, lib/assets.swc, lib/assets.swf - used for assets and art

Added features:
Using .swc for assets instead of loading bitmaps.
Changed tile system from 0 to i, instead of -i/2 to i/2. No reason for the former.
Added cellHolder for holding cells, so you can move it independently.
Added cell array.
Added the following functions in GameScreen.as: snapToCell(), setCell(), getCell().
Changed tile art. It is prettier now, and has more depth.