enhanced list move/merge/split

[ctengel]

Single POST /lists/id/bulk (or merge)

Options:

• merge-into: list ID to merge split cards into, default could be a new list... Or just require consumer to create first
• delete: bool - delete this list after the merge...or require consumer...
• some kind of before or after selector to essentially split the list
• may also want a category selector

Originally posted by @ctengel in #93

MVP had only basic API: source and destination list ids

prob do this in conj with #98

also may want way to pick where in new list the stuff goes