Patch that ports latest Database.updateAttachments from iOS to support the no_attachments column on the revs table. This impl has one difference from iOS. The updateAttachment method explicitly sets the revpos of the updated attachment, on iOS I can't determine where this happens yet.
Further alignment to iOS imll
Added placeholder for canonical rev id generation
Fixed logic issue that caused attachment tests to fail with this fix
Fixes issues with unit tests
Minor cleanup
Merge pull request #144 from couchbase/issue_132

Issue 132