Expose recursive_round function

[pjhartzell]

Related Issue(s):
None

Description:
Pulls the recursive_round() function out of round_coordinates(). Being able to access recursive_round directly is useful in cases, e.g., where you'd like to round coordinates prior to creating an Item or Collection.

PR checklist:

• Code is formatted (run scripts/format).
• Code lints properly (run scripts/lint).
• Tests pass (run scripts/test).
• Documentation has been updated to reflect changes, if applicable.
• Changes are added to the CHANGELOG.

[pjhartzell]

@gadomski Does this need a changelog entry? It is just an edit to an unreleased feature (the round_coordinates utility function that operates on Items and Collections) that doesn't change the functionality of the feature.

[gadomski]

Does this need a changelog entry?

It adds a new free function to the public API so I'd say yes.

[gadomski]

Since we're adding it to the public API, we should probably add some unit tests to verify its behavior.