Overhaul Transport Modules

[madoar]

Currently we use inside the admin and client transport modules primitive datatypes and Strings to map fields like:

• minimumAge of games
• releaseYear of games
• lendTime of games and identity cards

To allow a better handling of the values on the Java/Scala side we should add XmlAdapter implementations for the Year and LocalDateTime classes to allow serializing them directly via JAXB.

See also #334