CRM-20199 Remove poor join on option_value table when doing contribution search.

CRM-20199 Remove poor join on option_value table when doing contribution search.

This involves setting payment instrument to exportable & remove hacks that were used in
place of doing that, and adding new logic to the order by to allow it to order without
joining the option value table (using the field() function).

I have observed one small regression which is the Qill showing 'Payment Method ID'
instead of payment method. I'm committed to fixing that but I would push
to merge this in advance of that because we are in the best place in the monthly
cycle to merge this and that is a very minor fallout.