Issue #190 - enhance mock http client to remember previous docs sent via bulk_docs, and modify future _revs_diff responses accordingly.

https://github.com/couchbase/couchbase-lite-android/issues/190
Issue #190 - add testOnlineOfflinePusher() which verifies correct behavior after going offline and online several times.

https://github.com/couchbase/couchbase-lite-android/issues/190
Issue #190 - fix compile error in unit test

https://github.com/couchbase/couchbase-lite-android/issues/190
Merge branch 'refs/heads/issue_190'