Allow its-* plugins to register actions of their own More and more actions are created in the project. Each one requires hundred of lines of modifications in its-base. Also most actions will only be implemented in a unique its-* plugin implementation. This change allows its-* plugin to expose new actions without requiring the modification of its-base. Change-Id: Ib9993cc0643f1524ce31905ebf71e1fe4994c9fa