Add check for minimum bash version supported
Import sub-commands from external sources.

So users can add custom sub-commands easily.
Rename *.bash to *.in; fix lib install
Make 'help' useful when no args are passed
Import sub-commands after geometry processing.

Certainly after command line option processing, otherwise the debug line
wouldn't work.  We want to give the sub-commands sources as much
information as possible, so source them as late as possible.
Documentation for registering sub-commands
Remove option -l: superseded by sub-command 'help'
Set version to 2.0.0-rc3