Additional actions for OMG

[reload-deploy]

When doing a rollback it would be nice if Deployotron could perform additional tasks such as:

1. Set the existing site offline before the rollback is initiated
2. Keep the restored site offline (if it is in fact online)
3. Clear caches after the site has been restored. This is especially usefull when using non-database cache backeds
4. Update VERSION.txt
5. Restart Apache and Varnish
6. Set the site online again

[richardbporter]

I've got a use case for the OMG command updating the VERSION.txt. Could/should this happen? Is it as easy as adding 'CreateVersionTxt' to the ActionMapping?

[xendk]

Should be. I guess most of the deploy actions makes sense to run in OMG too.

[xendk]

Closed by #44