Allow for complex custom types

[JeremyBOB81]

Currently if we implement a custom type, the extractor will only cater for simple custom types. We need to add functionality for complex types also.

[JeremyBOB81]

So attempt 1 at the xml parser didn't really work, the complex lists caused a problem. I've changed strategy a bit and instead of dealing with parsing the individual nodes myself, I'm going to rather create a ComplexTypeSectionHandler that returns the XmlNode of the section. The ComplexTypeExtractionStrategy will then just take the node and do a standard serialization parse to convert it to the complex object.

Initial testing looks really good on this and it actually massively simplifies the code.

[JeremyBOB81]

Current code is in develop. I have a few new unit tests I want to create to ensure I'm happy with it before I close this ticket.