[Redesign] Clean up <select>
Summary: Ref T8099, Ref T8449. Adds a min width to selects (can't think of anything this breaks in ui) and adds space around space select.
Test Plan: Review a number of selects in different UIs, forms, dialogs.
Reviewers: btrahan, epriestley
Reviewed By: epriestley
Subscribers: epriestley, Korvin
Differential Revision: https://secure.phabricator.com/D13523