FRQ: extend functionality of frame.data() to accept lists

[kay-ro]

Proposed new feature or change:

The Frame s of Trajectory objects store all data and specific values can be extracted with frame.data() by supplying the wanted keys as arguments. But often it is easier to supply a list or array of keys which is not possible at the moment, therefore it would help to add a recursive call at the beginning of the function to accept lists as well as arguments.

if isinstance(args, (list, np.ndarray)):
    return data(self, *args, ptype = ptype, zerofill = zerofill, return_keys = return_keys)

• implement and check implementation
• update documentation
• add example