Fixes #132 - Added a clone operation

This clones the AR, attaches clones of the
originals host_parameters and then renders the "new" action, ready for editing.

The host_parameters must not use validate_presence of :host_id when using nested attributes.
Created a hidden :nested attribute to the form to flag this behaviour...

fixes #201 - Remove activescaffold from the domains page

added domain and common specific parameters.
this adds a similar functionality to extlookup.
the order in which parameters are processed is:
common => domain => hostgroup => host
where the latest occurrence of a parameter takes priority.