Issue #189 Prevent slow sandboxes from impacting the system throughput

- Close the filter/output input channel after the match runner loop exits so the
match runner input channel is properly drained.

- Add new metrics for the sandbox filters and updated the dashboard
	- total number of messages processed
	- a sample of the ProcessMessage() call average duration
	- the TimerEvent() call average duration (output)

- Monitor the filter's input channel buffer depth and message processing time.
If the sandbox is running slowly and it is blocking router, terminate it.
Incorporate review feedback

- rename the router Matcher management functions
- add protection for a nil output matcher since we are now removing them
- re-sync the dynamic plugin config code with the static config code
	- initialize the RetryOption struct
	- clean up the ticker initialization
	- pass the pluginGlobals to the runner
Merge pull request #190 from mozilla-services/issues_189

Issue #189 Prevent slow sandboxes from impacting the system throughput