Added perm relating to refund reasons
Added reasonnum col, allowed reason to be null, implemented key constraint with reasonnum col
added reason method, allowed reasonnum to be passed in, allowed reason to be null in check method, modified _upgrade_data to migrate reason col in cust_refund table to reasonnum col
added activate, renewal, term change, and refund reason_type classes
updated ui to use a dropdown of existing reason types instead of text box
added refund reasons to main menu
added refund reason_type class