MB-10640 UPR Stream Request and Stream Marker changes

Added new fields for stream req:
snap_start_seqno
snap_end_seqno

Removed:
high_seqno

Added new fields for marker:
start_seqno
end_seqno
flags

Change-Id: I4f7528f453e1f0c3021ab51f2173e111ed4a17e9
Reviewed-on: http://review.couchbase.org/36433
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>