We already know which list widget a `<th>`
tag is associated with when we set up the
event handler, so it's silly to read data
from the DOM to find that widget again
when the handler runs.
This commit eliminates a whole class of possible
errors and busy work.
02cfb47 removed a couple HTML tags that were
being used to sort the table. We fix this,
but disable filtering exports by marking the
input type as `hidden`. We use this approach as
it seems `list_render` doesn't like an
undefined `opts.filter.element`, which is
what happens if we simply remove the `filter`
key.
Steve Howell
Wyatt Hoodes
Rishi Gupta
Thomas Ip