Search builider does not allow >, < type operators on custom fields with option groups

While for many custom fields with option groups it doesn't make sense to have a gt, lt search, for others it does. For example, a field like "leadership level" with an option list of 1, 2, 3, 4 or 5 really needs a lt/gt search to be functional.

Since MySQL allows lt/gt searches on strings, it doesn't seem to hurt to add this.