Sidekiq initd

Description
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Adds `init.d` script support for managing sidekiq instead of using upstart (retains upstart workflow though for those who still wish to use it).

Also adds the `quiet_restart` functionality which waits indefinitely for the sidekiq worker to finish it's work (backgrounded if requested), upstart doesn't seem to allow as timeouts are required for upstart.
Nice. We should do this in the resque cookbook at some point.