_prepare_handler = function(registry, subkey, source){
        registry['ipython.'+subkey] = {};
        registry['ipython.'+subkey].help = source[subkey].help||subkey.replace(/-/g,' ');
        registry['ipython.'+subkey].help_index = source[subkey].help_index;
        registry['ipython.'+subkey].icon = source[subkey].icon;
        return source[subkey].handler;
    }
A bunch of `Advance actions` for IPython.
Cf `Simple Action` plus the following properties.

handler: first argument of the handler is the event that triggerd the action
     (typically keypress). The handler is responsible for any modification of the
     event and event propagation.
     Is also responsible for returning false if the event have to be further ignored,
     true, to tell keyboard manager that it ignored the event.

     the second parameter of the handler is the environemnt passed to Simple Actions