feat(olddataset): add classes and read from kml

closes #14 (closed)

closes #15 (closed)

• add base classes for dataset and image : BaseDataset BaseImage : used for common data from pva dataset/image and old dataset/image
• add new classes for old dataset and image : OldDataset OldImage
• update kml_reader.py function to support OldDataset / OldImage with an boolean option old_format
• add fixture for old dataset and image