Convert priority string to integer. If not error in foreman/lib/tasks.rb <=> other.
Merge pull request #1 from grimme-atix-de/priority2int

Convert priority string to integer. If not error in foreman/lib/tasks.rb...
Change AR::Observer to basic AS::Callbacks registration

This fixes the case where AS::Callbacks are used for host build/provision
hooks, which don't fire on AR::Observers.

Change include method to hook loading of missing constants to handle class
reloads in development.  Thanks to Ivan Necas for this technique.