Refactor of API to be more testable and use JSON.NET serialisation

#4 Determine JSON serialisation to use within the API
- Removed the FemahApiHttpHandlerFactory so we can override
ProcessRequest in the HttpHandler and use the far more mockable
HttpContextBase
- Added 3 basic unit tests for the API
- Took a dependency on the the JSON.NET serializer
- Implemented tolerant JSON reader tests as per issue #4