Deploy across an entire web cluster

Adds deploy, undeploy, and redeployAll to webapp cluster entities (DWAC and ControlledDWAC).

Also fixes some issues noticed in how tasks are tracked and displayed.
There is a race here for setting the attribute. But I'm not too concerned about that. I wrote in some downstream project (can't remember which off hand!) some code to get+set the attribute of type List atomically. Might be worth having some utility for that - but can think about it in a different PR.