Try to guess a name for the 'Add to Dashboard' workflow

Summary: Ref T5307. Just makes the dialog a little easier to use. Picks a name if we already have one.

Test Plan: Test a builtin, custom saved, and a new advanced search (no name).

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T5307

Differential Revision: https://secure.phabricator.com/D17523