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. 
Honestly, not sure there, hence the heck. I dont think we have run into that issue before, but then again we were only storing basic strings in there and not a blob. maybe that makes a difference. @dfish3r might know more of course.