Create deserialization methods for UDDF

[pridkett]

dc2uddf has a collection of methods that may be useful outside of the context of simply dumping a set of dives (for example, fixing initial pressure samples, truncating dives, etc). To make this more useful we should include code that allows deserialization of uddf files. This will also help ensure that serialization is working properly as a dive collection should be able to be serialized and then deserialized to the same state.