Be able to reset a rule back to it's default state and have that reflected without refresh as an editor

[stuartromanek]

#15 Makes progress towards reverting palette rules back to their default state but to reflect that to an editor using palette we need a way to remove all the selectors in question from the on-demand style tag so they get the correct visual feedback.

[stuartromanek]

Potential non-parsing solution: clear out the generated inline stylesheet and refresh the real resource, which should get all new changes and properly ignore the new null rule