Added master command

The lmc command provides an interface for each function.  E.g. 'lmc
assemble' runs the assemble and 'lmc console' runs the GUI.  Help
functions were added so that 'lmc help' shows a top-level help message
and 'lmc help <action>' shows a message specific to <action>.

Moved all code but the master command to a package.  Tests' module paths
were updated.

Added setup.py.  Added generated files to .gitignore.