Tidy up executables (fixes issue #195)

Put the user scripts (front-end command and sub-commands) in bin, and
add that to package.json.

Add various other bits of useful metadata to package.json.

Remove the unneeded serve.sh.

Move all the developer scripts into dev-scripts/

Adjust scripts and documentation as necessary to refer to new locations.
Improve a couple of bits of documentation
Fix commander’s arguments call to be fluent

Write command definitions in fully fluent style