Fix a typo in an error message
Merge pull request #403 from Collaborne/typo-start

Fix a typo in an error message
Split the start/stop actions from the river start/close methods

The RiversService will invoke #start()/#close() when the river itself is started/stopped. However
we also have our internal status (controllable via REST, and driven by the StatusChecker), which is
semi-independent from that.

Split those two lifecycle actions:
River #start()/#close() now only manages the status thread itself
MongoDBRiver #internalStartRiver()/#internalStopRiver() is invoked by the status thread

This fixes first of all #406, as we're no longer deadlocking inside the initial listener thread. As a side-effect
it also fixes a potential inconsistency between the status of the river as seen by us, and the status of the river
as seen by the RiversService.
Start the status checker when the river is merely administratively disabled

A later REST request can be issues to start the river.
Do not force the river status in #close()

When we restart the river should come up in the same status as it was before, to switch a river
into the "stopped" state it must be explicitly done so using the REST API.
Change #internal{Start,Stop}River() to package protected

These methods aren't for external usage, but rather form a contract with the StatusChecker thread only.
Make it clear that "disabled" means "nothing will happen now"

Suggested-by: @benmccann