MB-100: Remove unused parameter from queueDirty function

Change-Id: I51a13878eb975835ae44edf48e986f4be9c1edea
Reviewed-on: http://review.couchbase.org/27153
Reviewed-by: Jin Lim <jin@couchbase.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
MB-8516: Change seqNum to revSeqno in QueuedItem class

We have two different sequence numbers that we will be working with
in ep-engine and it is very confusing to figure out which on we are
talking about when the variable name is specific. The xdcr sequence
number should be revSeqno when it is used in order to distiguish it
from the by sequence number.

Change-Id: I8e2a2764deb9ffc01d0dd43c9ee5d950196a88aa
Assign sequence number in ep-engine

Change-Id: I10e841e2c6f52d4543a1feb8c708a697226fea3f
Sequence numbers are assigned through the CheckpointManager

Change-Id: If3fdf08e1091ad36ea8bcd30b10cd3803db009ae
Add the by sequence number to the tap engine specific section

Change-Id: I501bd9b044e929bda324dd8cb2c2370c9900029f
Backfills are only from disk

This removes the memory backfill that was used when more than 90%
of the items are resident in memory. We cannot use that mechanism
anymore because we need to ensure that items are sent in order of
increasing sequence number.

Change-Id: I6d1e1994ce558d3cba45693d82e7d51c280b0704