Action Watcher can optionally filter on prefix
Add tests for Unit.WatchActions
Refactor filterFn to make loop() function cleaner
one more refactor; simplify watcher struct
1. Don't use Tags internally 2. Log unexpected key value in watcher filterFn
Merge pull request #132 from johnweldon/unit-action-watcher

Unit Action Watcher

Add Unit.WatchActions for filtered action notifications by Unit