Add capability for compaction on local update
Add capability for compaction on local update

Prior to this commit, there was no functionality for a custom compactor
to know if the local database had been updated. This commit adds a
local_updated event, which will inform custom compactors when the local
tree has been updated.

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,apache/couchdb-couch,cloudant/couchdb-couch,cloudant/couchdb-couch,cloudant/couchdb-couch,fkaempfer/couchdb,apache/couchdb-couch,apache/couchdb-couch,fkaempfer/couchdb,fkaempfer/couchdb