We want to be able to search for available system actions, so
rather than tracking each action in a separate property, store
them in a single map that can be searched in a generic and clean
way.
https://bugzilla.gnome.org/show_bug.cgi?id=691900
In anticipation of showing the system actions in
the search results, it is fit to move action
specific code to its own module in order to
reuse it.
https://bugzilla.gnome.org/show_bug.cgi?id=691900