First cut of progress bars (PHUISegmentBarView)

Summary:
Ref T10288.

I couldn't figure out how to reasonably get the interior right borders to round like the mock, but I think this is otherwise mostly faithful. Feel free to fix stuff.

Test Plan:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10288

Differential Revision: https://secure.phabricator.com/D15219