Make default and hidden columns in Workboards more clear
Summary: Fixes T6469. Changes the default icon into text instead. Added the text to hidden boards and now display when reordering as well.
Test Plan:
Moved a bunch of columns, tested reordering. Seems more clear.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T6469
Differential Revision: https://secure.phabricator.com/D10784