assign Collection to Item outside of payload

[ping-e84]

The Task assign_collections method will assign Collection(s) to Items in the payload Features list using collection_matchers. Items that exist independent of a payload (for instance a newly created Item) do not have such an option. Create a method that will do essentially what assign_collections does, only without requiring the Features list. Or, maybe, change assign_collections so that it can accept an Item or list of Items, and just handle it from there...