Remove property "id" from Workboard View controller

Summary: Depends on D20626. Ref T4900. On this controller, "id" is a separate property, but serves little purpose and complicates separating state management. Remove it.

Test Plan: Bulk edited a column, managed filters, did show/hide on columns, edited a column.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T4900

Differential Revision: https://secure.phabricator.com/D20627