Issue #253 enhance mock infrastructure

https://github.com/couchbase/couchbase-lite-java-core/issues/253
Issue #253 add takeRequestBlocking method

https://github.com/couchbase/couchbase-lite-java-core/issues/253
Issue #253 test which reproduces issue

https://github.com/couchbase/couchbase-lite-java-core/issues/253
Issue #253 minor cleanup to test

https://github.com/couchbase/couchbase-lite-java-core/issues/253
Issue #376 improve unit test to remove sleep and wait for PUT checkpoint request.

https://github.com/couchbase/couchbase-lite-android/issues/376
Issue #253 fix issue with mocking framework that was causing it to return 406 errors for sticky responses.

https://github.com/couchbase/couchbase-lite-java-core/issues/253
Issue #253 make it easier to debug async task count issues.

https://github.com/couchbase/couchbase-lite-java-core/issues/253
Modify tests to take feed type into consideration w/ regards to mock _changes behavior.

https://github.com/couchbase/couchbase-lite-java-core/issues/255