bathtub, oven, cupboards pushable
Changed itypes to use a map instead of a hash, as well as some required changes elsewhere, like in bionics, to make that work.

This is a significant refactor. It is the first step on moving items out to an external data file, and allowing more control over how items work later on.
Remove some commented out code.
Remove trailing whitespace.
Correct handling of flamable liquids.
Merge pull request #306 from wito/more-pushables

Just makes a few more things pushable.
Merge branch 'master' into batsys-fix