[GEOS-6729] Add a flow control provider notion allowing extension to setup different flow controllers per user/request
[GEOS-6731] Add response headers to make delays evident
Fixed some minor typos
[GEOS-6730] Allow request rate limits in control flow extension (along with some refactors to avoid code duplications)
Merge pull request #791 from tbarsballe/docs

Fixed some minor typos
Merge remote-tracking branch 'upstream/master'