In host's edit page, show the source for the value of puppet class parameters

Currently, on the edit hosts page, under the parameters tab, if a parameter was overridden in the host's hostgroup (or that hostgroup's hostgroup), the additional information popup for that parameter says "Matcher: hostgroup."

![screen shot 2014-08-07 at 5 33 25 pm](https://cloud.githubusercontent.com/assets/4042349/3851389/fc038b6e-1e93-11e4-9e80-41d775df765c.png)

This is not very useful because the parameter's value could be coming from the hostgroup or a grandparent hostgroup. It would be more useful to display the actual hostgroup's name so that we know precisely from which parent the parameter's overridden value is coming from. 

![screen shot 2014-08-07 at 5 39 05 pm](https://cloud.githubusercontent.com/assets/4042349/3851415/7660d574-1e94-11e4-822d-df05ebc84b39.png)

Unfortunately this will break i18n lookups, as it will store a value of "domain(example.com)" and later when we try to translate it, this won't be found (only the string "domain" should be translated).

I think to fix this, you should pass :source and :source_name here, e.g. `:source => N_('domain'), :source_name => domain.name` and then in app/helpers/common_parameters_helper.rb where we display the source, do:

    content_tag(:span, :class => "help-block") { popover(_("Additional info"), _("<b>Source:</b> %{type} (%{name})") % {:type => _(value[:source].to_s), :name => value[:source_name]})}