Indent multiple items from the same application in Quick Create menu

Summary: Ref T10004. Happy to take another approach here or just not bother, this just struck me as a little ambiguous/confusing.

Test Plan:
Before, not necessarily clear that the "Create Task" header only applies to the first few items.

After, more clear:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10004

Differential Revision: https://secure.phabricator.com/D14815