Modify 'gear restart' to do all cart instances

Add --all option to 'gear restart' to allow it to restart all instances
of a cartridge across all the app's gears

Call update_proxy_status before/after restart to rotate the gear out of
the proxy, then restart, then rotate back in
Merge pull request #37 from ncdc/gear-restart-rolling

Modify 'gear restart' to do all cart instances