Case roles (relationship types) where either or both contact types are a subtype of Individual should be supported

Currently if you assign a subytpe of 'Individual' as Contact A or Contact B in a relationship type used in Cases, when you try to assign a contact to that case role it appears to work, but puts the string 'undefined' in the Contact Name column of the case roles table (and doesn't actually create the relationship).

1. Fix processing so that contact subtypes (of Individual) can be used for case role (relationship) assignment.
2. Fix the error handling so that if a relationship type is configured for a case role that is currently NOT supported (e.g. one or the other side of the relationship type definition is a Household or Organization) - we give a helpful error message and then return to the main CaseView page:

"The relationship type definition for the $relationshipTypeLabelBtoA case role is not valid. Both sides of the relationship type must be an Individual or a subtype of Individual. You can review and edit relationship types at <a href="$relTypeAdminLink">Administer >> Option Lists >> Relationship Types</a>."