Uniter API now has WatchActions

This commit adds state/api and state/apiserver endpoints for
WatchActions.
Added extra bits to api/uniter TestWatchActions
apiserver uniter_test TestWatchActions now ensures that the watcher has appropriate results when actions go through
WatchActions no longer discards events
Extra tests on api/uniter WatchActions
Removed spurious WatchActions test
Addressed extra test cases
Testing preexisting Actions case
Now parses unit tag directly
ActionsWatcher now retrieves pending Action ids in the initial event.
Fixed behavior of state/api/uniter test to reflect new Action query.
Addressed missing comments in Actions additions
Merge pull request #141 from binary132/actions-uniter-api-watcher

Uniter API now has WatchActions

This commit adds state/api and state/apiserver endpoints for
WatchActions.
Fixed up ActionEvents worker/uniter/filter tests to reflect AddAction changes
Fixed test behavior of worker Filter to account for change to Action query
Added filter test to ensure pre-queued Actions are properly received on worker event filter