disable middlemanagers based on worker version
address code review
fix broken UT
docs for updating
add more stuff to docs
log errors in asyncForwardingServlet
fix enabled endpoint
Merge pull request #640 from metamx/disable-worker

An alternative way to disable middlemanagers based on worker version
Merge branch 'master' of github.com:metamx/druid into cleanup-ingest
Merge branch 'cleanup-ingest' of github.com:metamx/druid into cleanup-ingest

Conflicts:
	server/src/test/java/io/druid/realtime/firehose/CombiningFirehoseFactoryTest.java