Add elasticsearch module and role.

I make three changes from the default debian install, all of which are
recommended by
http://www.elasticsearch.org/guide/reference/setup/installation/
1.  Make heap size configurable in the module but default it to 2G which
is good for labs and probably beta.  I just guessed a big number for
production and imagine we'll change it.
2.  Turn on mlockall.
3.  Turn on logging to see if mlockall works.

Change-Id: I0d764c34c7a35f53fa0b22a4732697ab98ff70ec
Merge "Add elasticsearch module and role." into production