Kwcoco

Added
* Can now load do delayed loading of data in auxiliary space. (throws an error
if multiple auxiliary streams are mixed)
* issubset issuperset for FusedChannelSpec
* union for FusedChannelSpec and ChannelSpec
* `find_asset_obj` for CocoImage
* Added quantization spec. CocoImage.delay will now return a dequantized image
if quantization metadata is available.

Added
* verbose flag to perterb function
* Added new exceptions `DuplicateAddError` and `InvalidAddError` to better
indicate why an add image/category/annotation failed.

Changed
* Combine measures can now take an explicit set of threshold bins to accumulate to.

Fixed
* Bug in delayed with nodata

Added

* `path_sanatize` to `kwcoco.ChannelSpec` to make a path-safe suffix for a filename
* Add experimental `_dataset_id` function to `kwcoco.CocoDataset` for unique
but human interpretable dataset identifiers.

Changed

* Conform now adds width / height to auxiliary objects
* Enhanced the `CocoImage.primary_asset` function
* gdal reader now uses an auto nodata mode, somewhat experimental.

Added
* Caching mechanism for model hashids

Changed
* Minor improvements to confusion measures.
* AP / ROC curves now report real/support using concise SI for large numbers

Changed

* Removed old Python2 constructs
* Modified multisensor to use concise channel codes
* Moved `LazyGDalFrameFile` to `kwcoco.util.lazy_frame_backends` to experiment with different image subregion loaders