Implemented new dynamic context search action group mechanism.

All blueprints can similarly to registering menu entries register context search actions for one or more groups. These are then used for generating context search action dropdown menus for various items like IP addresses, groups, etc. One of the example use cases is the event search result page, which contains action search menus for each of the displayed IP address, abuse group, category, etc. (Redmine issue: #4321)