Reorganized the modules, move DefineCommand into new module define.py ...

This avoid circular dependencies.

Various bugfixes on the interpreter.

Wrote most of the interpreter, need to find bugs now to get it to work.

A lot of work on World and the interpreter. ...

This is the applicative branch - I cut out the OptionCommand class, using
method calls to stored function names for options instead.

Added the banner, wrote interactive starting mode.

Significant progress, especially in place.py and parser.py

Wrote example.atl, the reference file for the Atlantis language. ...

Started on main code.

First commit of Atlantis to git. ...

Not much to see yet.