financial#2 Support payment processor title if configured on Contribution Pages

Per financial#2 we agreed & added a 'title' field to the
civicrm_payment_processor table some time ago for exposure on front end forms.

We haven't actually done this, or made it UI configurable.

This fixes that for contribution pages & adds comments pointing out the tidy up
needed to make it similarly available on the events page.

Once done we should add to the payment processor form