R1:55072a264002

Move all ListFilter buttons into crumbs

Summary:
Maniphest and Owners still have green ListFilter buttons, which have looked awkward for a while and are extra-awkward after D4447. Move them into crumbs and remove the ability of ListFilter to support buttons.

The actual implementation can be simplified too now.

Test Plan: Looked at Owners, Maniphest. Clicked create buttons. Looked at UIExample.

Reviewers: chad

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D4451