Permit users to touch maniphest.points

Summary: Ref T4427. Seems fine / not egregiously broken.

Test Plan: Edited points configuration. Tried to set a bad value. Set a good value. Persued examples and help text.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4427

Differential Revision: https://secure.phabricator.com/D15256