Adds Wizcorp to PoweredByMesos page.
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.
First try to fix #1571. Propagate shutdown timeout to Executor and CommandExecutor via env variable. Remove escalation constant for command executor.
Second try to fix 1571.
Third try to fix 1571. Move shutdown adjust timeout logics into utility function, improve comments and style.
Fix build errors.
Add a comment about ShutdownProcess design.
Add tests for graceful shutdown.
Add and fix comments.
Fix graceful shutdown test on Linux.
Add more comments.
Update comments.
Rename functions adjusting timeouts; introduce a check; update comments.
Refactor timeout adjusting function.