fixes #917 modified: app/controllers/common_parameters_controller.rb modified: app/models/common_parameter.rb

Signed-off-by: Marcello de Sousa <foreman-dev@area151.com>

fixes #207 - remove activescaffold from Parameters settings

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.