XDCR Advanced Filtering Test Feature to add collection namespace

XDCR will allow an optional pair of Key-Value to be passed in as part of the REST call for regex validation.

Right now, regexValidation should already be passing in the following KV's:

1. bucket
2. expression
3. docId

This MB will add two new KVs:

1. scope
2. collection

The two new KV's should be sent in as a pair. The pair is optional. If they are not sent in, then it'll behave as before. (XDCR would look for the doc in the default scope default collection on the bucket specified).

Otherwise, XDCR will look for the document name in the specified namespace (with the new pair)