Rename "open" status to "acknowledged"

Currently their is very little conceptual difference between "new" and "open". The difference is really just that someone has "accepted" or "acknowledged" the issue. I propose that what is currently called the "open" status be renamed to "acknowledged" to better reflect the action.

"open" should still be a button on the UI, but (as it does currently) should show results for any tickets that are not any of the closed states (ie. lists both "new" AND "acknowledged")