Allow directly setting keys on the packet classes

[qixils]

The class has sort of ballooned in size with CC2 and it's become quite unwieldy to support each new field. The removal of constructors has helped but it still takes a lot of time to create the parameters, the getters, the builder setters, the builder getters, the javadocs, the unit tests, etc. Some sort of Sponge-like key system for building and getting data from these classes would make development a lot simpler.