MB-23182: Recording batch level stats using new ghistogram API
MB-23182: Recording batch level stats using new ghistogram API

+ Adapting the way to record batch level stats - key sizes and
  value sizes using a new API in the ghistogram library.
+ Pre-req: http://review.couchbase.org/#/c/74814

Change-Id: I4e44103e9726f0e9b1e7a196ce6e4c2a8d6a9dc0
Reviewed-on: http://review.couchbase.org/74815
Reviewed-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>
Tested-by: abhinav dangeti <d73ef2279de6577f7bf081737ee47554bbb7dc82@couchbase.com>

steveyen/moss,steveyen/moss,couchbaselabs/moss