JVMCBC-54: Add checkstyle.

Motivation
----------
We need proper checkstyle rules that need to be enforced across the project.

Modifications
-------------
This change adds the styles we agreed on for now, separate commits will follow
with the actual code changes.

Result
------
Consistent styles!

Change-Id: I9fc563e42e1165f143b2272bc9c15d211b815796
Reviewed-on: http://review.couchbase.org/43120
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>