Bring back contextual actions

Contextual actions depended on appletscript. what the old thing did was taking all the actions accessed by AppletInterface::action("name") by qml (but not c++) and adding them in the context menu. This restores 100% of the behavior with an ad hoc property set by appletinterface

This will have to be overhauled when Plasmoid will have to become Applet *