Scope entries to their replicator db

Add db name to the doc id to ensure they are unique.

BugzID: 177426
Better handling of _replicator db deletes

When a _replicator db is deleted all running replications based on that db
need to be canceled.

BugzID: 17426
BugzID: 17571
Merge pull request #18 from cloudant/17571-17426-better-replicator-db-delete

BugzID: 17426
BugzID: 17571