fix debug scripts handling of no fields in a watchman subscription
fix debug scripts handling of no fields in a watchman subscription

Summary:
Fix default fields to be watchman default fields. There are existing
subscriptions at Facebook that have no fields specified - so, let's handle them
properly!  Add 'state-only' option to limit output to state-enter and
state-leave PDUs.

Reviewed By: wez

Differential Revision: D6025649

fbshipit-source-id: a8495883b3e2acf41ca88fbb8977c3e767edef2f

wez/watchman,kwlzn/watchman,nodakai/watchman,kwlzn/watchman,nodakai/watchman,nodakai/watchman,kwlzn/watchman,kwlzn/watchman,nodakai/watchman,nodakai/watchman,kwlzn/watchman,wez/watchman,wez/watchman,nodakai/watchman,wez/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,wez/watchman,wez/watchman,nodakai/watchman,facebook/watchman,wez/watchman,facebook/watchman,wez/watchman,wez/watchman,facebook/watchman,kwlzn/watchman,kwlzn/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman