Summary:
Dropdown menus are entirely dynamic right now and use custom CSS. Begin rebuilding them to use ActionList CSS.
This introduces PHUIX components which are basically JS copy/pastes of the PHP PHUI components, just implemented in JS.
We have two other dropdowns: policy controls and one in Conpherence. I'll convert those, then implement D8966.
Test Plan: {F150418}
Reviewers: chad, btrahan
Reviewed By: btrahan
Subscribers: epriestley
Differential Revision: https://secure.phabricator.com/D8973
