Disabled filter form inputs while requests are pending.

This is probably the worst kind of feedback to ever give to the user. At least
I excluded the element which has the focus because the latter gets lost in
Chrome otherwise. Still very very bad interface.
Migrated to jquery-1.11.1 and added source map.

It looks like work and I was tired of error messages.
Disabled filter_documents from running in parallel.

This works around turning off the filter form inputs as introduced in
7ff4a88d934df. The remainder of the argument list is stored into
filter_documents.next. If the function is already running, filter queries are
attached to that property and will be attended to as soon as the first ones
have been processed.
Inserted more spaces because it looks like work.
This applies some make-up on my disgusting code.

I aliased recall_arguments to filter_documents.next, so I might just use it for
the initialization as well. And I renamed it to stashed_arguments. It still
looks horrible and disgusting.
Simplified tail recursion to one argument.

Because I just need one argument to check if the filter is already enqueued. It
still is ugly ugly ugly code.
Simplified signature used to continue tail recursion.

I just could as well use recall_arguments instead of recall_arguments[0], if I
need a tag to tell filter_documents to go on with the tail recursion.
However, filter_documents isn't called without any arguments at the very end,
so the part where the viewport is updated had to move down, where new_filter is
set (or not).
Changed description from recall_arguments to plain 'commands'.

I've looked at it and its purpose has changed from an argument list to a queue
of commands that must be executed in order. So makes it a little clearer
without writing too much comments.