MB-7470: Make mutation_memory_threshold configurable at runtime

The engine parameter "mutation_mem_threshold" represents the
threshold (%) of a bucket quota in accepting incoming mutations.
This change makes this parameter configurable at runtime.

Change-Id: Ie5b26ab264096654f1074df5f00f53d50cbe4830
Reviewed-on: http://review.couchbase.org/23617
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
MB-7354: Provide an aggregated meta data stat

This makes it easier for the ns_server team since they don't
have to do the aggregation themselves.

Change-Id: I5a6f3dfdd63808a88891481d04ad86811be5ad4c
Reviewed-on: http://review.couchbase.org/23618
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
MB-7455: Fix ep-engine version to allow override for releases

The script was broken that allowed us to override the normal
git version that is used automatically. This change is
neccessary for production builds to reduce confusion when
looking at stats.

Change-Id: I9bc893beaa9f9ab057a0a8dd300933358e1acccb
Reviewed-on: http://review.couchbase.org/23664
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
MB-7460: Don't double print watermark stats

We have these in the config so we don't need to explicitly print
them.

Change-Id: I23e25849c61c1080a850ab72a0038197c9e53aeb
Reviewed-on: http://review.couchbase.org/23667
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
MB-7486: Couchstore stats should be resetable

Change-Id: I46e4fc3b1003caf3602e542467c3e7590388ebb2
Reviewed-on: http://review.couchbase.org/23694
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
MB-7487: Add a bulk size histogram to couchstore

Change-Id: I32bf2d93378035f57881e4b7ecbebc44bdf430a7
Reviewed-on: http://review.couchbase.org/23695
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
Merge remote-tracking branch 'gerrit/2.0.1'

Changes:
  MB-7470: Make mutation_memory_threshold configurable at runtime
  MB-7354: Provide an aggregated meta data stat
  MB-7455: Fix ep-engine version to allo override for releases
  MB-7460: Don't double print watermark stats
  MB-7486: Couchstore stats should be reseable
  MB-7487: Add a bulk size histogram to couchstore

Change-Id: I22ec04afd24a27cfe06f9d1ed88d58a9ab882aca