Fix for #3: uncluttered command.py

command.py was obviously going to get too cluttered to be of much
use so I decided to split it early. Each command gets its own module
now.

It's fairly dirty and not very idiomatic, but I don't know enough
Python to make this lispy-clean, nor do I intend to learn it to such
an extent.

Signed-off-by: Weland Treebark <weland@blinkenshell.org>