Most relevant processors/commands

[rtripault]

Add most useful processors as commands and a few "interesting" ones :

• [x] reset a user password (sending her an email to validate the password change)
• [x] disable a plugin (either providing its name/ID)
• [ ] install a new Revo instance (with the ability to define a "template" for paths)
• [ ] upgrade a Revo instance
• [x] download & install packages from providers
• [x] list packages having upgrades available
• [x] backup a Revo instance (fits into a third party component/library)