Add simple JsonShell

[LecrisUT]

Adapted the python shell to make a simple json reporter.

Analyzing how this implementation behaves shows a few issues:

• The reported json object represents only the actions, not the current state of the module. So then what should the json interface report:
  • Specific actions of set/unset/shell_function etc. as specific keys to the json object? Then the consumer would have to keep track of the state of the environment variables setting/unsetting/updating
  • Expand the base table in the lua script and just output the final state
• Commands like module list do not produce a meaningful tbl to be exported as json

[rtmclay]

This pull request has been merged on to the testing branch. Please try the Lmod testing branch to see if it works for you.