PROPOSAL: Add HOSTING_TASK_CANCELLED task status to show users that a task was manually stopped.

There are two cases where a task can be manually cancelled:

1. User clicks "Cancel" on a queued task. This triggers hosting_task_cancel() . The task is set to "Warning" with no indication about what happened.
2. User clicks "Update Status" button on a running task. This triggers hosting_task_update_status_form_submit() . The task is set to "Succcess" with no indication about what happened.

The "Update Status" text on the button is confusing as heck, I changed it to "Cancel" in devshop, but that's for another issue.

I propose we create a new task status: HOSTING_TASK_CANCELLED to indicate a task was manually cancelled in either of these two ways.

Thoughts?