Add support for elasticsearch 2
Maniphest Tasks: T146843
Adds a new config that is used to tell which version elasticsearch you
use, for example if you use elasticsearch 1, then you put in there 1, and
if you use 2, then 2.
@EBernhardson helped alot with figuring how to get it to work with
elasticsearch 2 properly.
@mmodell helped with helpig me creat a config we could use.
Reviewed By: mmodell
Subscribers: Aklapper, mmodell, EBernhardson
Differential Revision: https://phabricator.wikimedia.org/D388