Add filters to task list

[JeanMertz]

After implementing #8, #9 and #10, the list of tasks can become quite cluttered, especially if you have a lot of one-click tasks created from the same regular task, and thus sharing a similar search keyword among them.

One solution is to be able to filter the search results based on the "task types":

We should probably keep this a client-side implementation, and simply show/hide pipelines based on the active tab, and the types of tasks shown. (see: #19)

Bonus points if we persist the selected filter across browser sessions.

[JeanMertz]

This should support deep-linking, see #14.