This is a convenience function to create a number of actions and add them
to the action group.
The "activate" signals of the actions are connect to the callbacks and
their accel paths are set to <Actions>/group-name/action-name.
Mapping is:
([ "name": string,
"stock_id": string,
"label": string,
"accelerator": string,
"tooltip": string,
"callback": function(callback)
"data": mixed
]);