Added Java replicated log implementation of State.

Review: https://reviews.apache.org/r/24341
Added functionality to create SVN based diffs of arbitrary strings.

Review: https://reviews.apache.org/r/24535
Added DIFF to the replicated log state storage implementation.

Review: https://reviews.apache.org/r/24536
Ensured post-reviews.py added newline between subject and body.
Updated svn::diff/patch to use newer versions of functions.
Added --with-apr and --with-svn to libprocess configure.
Added --with-apr and --with-svn to Mesos configure.