Basic "Install Dashboard" workflow

Summary: Ref T12264. This allows users to install a dashboard they are viewing to their personal home menu or as a global home menu item. Has some basic ability to be extended later for maybe projects.

Test Plan:
Build a dashboard, click "Install Dashboard".

• As user only get personal option
• As HomeApp edit person, see both options
• Try installation as either, with and without label set
• Fake "global" form as user, get error
• Don't set anything, get error

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12264

Differential Revision: https://secure.phabricator.com/D17492