JSON serialization of RegisteredService into LDAP

Handles https://github.com/Jasig/cas/issues/681

I striped down the `DefaultLdapMapper` so the entire service definition is persisted into a single attribute as JSON. There are setters that allow extending the serializer, and I also modified the tests to adjust the objectclass required. Some classes had to include getters for serialization to properly work. 
So, I guess somehow the attribute is marked as binary because `isBinary` returns true. I am not sure why the attribute is considered as binary. Does it depend on the nature of attribute value? I dont see any references to binary attribute config in the context.