Fix package comments for vtctl.
Remove -follow flag from mysqlctl, to be replaced by mysqlctld.
Create mysqlctld service for remote mysqlctl actions.

This is intended for use internally by vttablet, in cases when it cannot
directly access the mysqld process because they are running in separate
cgroups (containers). Since vttablet and mysqld can share files, many
actions can still be done directly by vttablet. However, starting and
stopping mysqld must be done from within mysqld's cgroup, so these
actions are executed remotely by mysqlctld.
Make clone test use mysqlctld to stop and start mysqld remotely.
Merge pull request #112 from youtube/mysqlctl

Create mysqlctld service for remote mysqlctl actions.