Add list manipulation features

Unless I've missed it, there doesn't appear to be any inbuilt way to handles lists, e.g.

- fetch a list by name
- save a list
- Perform list ops like difference, subtract, intersect, etc.
- delete lists
- get a list of lists

Referring to http://intermine.org/intermine-ws-python/intermine.lists.html#module-intermine.lists.listmanager might help to selec useful methods and gain parity for our packages