Workboards - let users delete columns
Summary: Fixes T4408. I had to add a "status" to colum. I think we'll need this once we get fancier anyway but for now we have "active" and deleted.
Test Plan: deleted a column. noted reloaded workboard with all those tasks back in the default colun. loaded a task and saw the initial transaction had a "Disabled" icon next to the deleted workboard. also saw the new transaction back to the default column worked.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: epriestley, Korvin
Maniphest Tasks: T4408
Differential Revision: https://secure.phabricator.com/D8544