Add functions to change plugin name, description and version.

- This allows to relink the plugin under a new name without
  having to use another step file by setting version 0 to trigger
  a unlink before setting it back to 2.
Add debugging helper script using mumble_link.

- step_link.py can step through a list of commands
  for the mumble_link plugin and execute them. See
  sourcetest.py for an example on how a step list
  might look like. Execute with:
	python step_link.py sourcetest
  The step list is imported so no .py ending!