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. 
It finally occurred to me why this is happening. You're serializing JSON with line feeds. The UnboundID provider sets the attribute as binary because the line feed requires base64 encoding per the LDIF spec. I'll raise an issue to investigate further.