Add support for List/Collection/Map in relationship valued JPA attributes

The wizard for adding a new relationship field to an existing JPA entity class could be enhanced to offer more types for that field. Currently only java.util.Set is supported, with the java.util.HashSet as the instantiated type. As per the JPA 2.0 specification, section 2.2:

Collection-valued persistent fields and properties must be defined in terms of one of the following collection-valued interfaces regardless of whether the entity class otherwise adheres to the JavaBeans method conventions noted above and whether field or property access is used: java.util.Collection, java.util.Set, java.util.List, java.util.Map

I have discussed briefly this idea on the IRC channel (I == lonely_koala).