Fix Membership: Get by Contact ID to actually support optional configurations. Add parameter mapping for membership type.

Since all the configuration fields for Membership: Get by Contact ID are optional, they should act like it. Consider the following setup:

This should return a membership of any type, of any status, in the default sort order, for the given Contact ID.

Also adds a parameter specification so you can search for memberships of the given membership type(s) from a parameter.