Convert list of tasks to use views

This is also done, but updated in my latest commit to now fully replace the previous, non-views approach and the AJAX has been updated to use the View.

It is still using a Node view, primarily because there is not yet a way of doing a View of tasks, but also because the Task node has all the information I'd want to replicate the previous list.

Does this cover this feature request? #1891808: A view for tasks' execution time If so it should just be marked as a dupe and merge the discussion here...

Not sure that it does, this is just replicating the existing tasks block and page as a view, that seems to be asking for something new.

Dealt with the other issue. Marking this one as fixed.