Added {to/from}_xml methods to IObject interface.
Update INSPIRE tests and fixtures
Fixed file modes for XML samples
Added `dictize_errors` as an option to validate
Added `to_xsd` method to IObject interface
Fixed #33
Merge with master
Added a simple Object serializer (JSON)
Added unit tests for serializers
Added unit tests for serializers
Implemented XML serializer for text field (draft)
Implemented basic XML serializers for fields (draft)
Attempt to implement XML serializer for Dict fields (problem with attributes on simpleType)
Implemented XML serializer for Dict field (with global type definition)
Implemented generation of XSD document for IObject objects (draft)
Implemented XML serialization for fields/objects
A 1st draft for XML serializers
Removed {to/from}_xml from IObject interface (replaced by adapters to IXmlSerializer).