Convert pledge search form to use metadata functions

Convert pledge search form to use metadata functions

This doesn't change anything of itself but is a pre-requisite for
- removing jcalendar instances
- supporting params in the url
- supporting appropriate wildcards on text fields (not seemingly relevant on this entity).

In addition it is a driver for cleaning up metadata for our eventual leap away from quickform.

In this case the change highlighted the need to define the html type on the converted field
(pledge_status_id