Kwcoco

Changed
* CocoDataset.dump now uses `safer` with `temp_file=True` by default.
* Initial steps to rename "auxiliary" to "assets" in a backwards compatible way.

Fixed
* Bug in valid region warp

Added

* Method to get the valid region for a CocoImage in image or video space


Changed

* CocoSqlDatabase is now lazy exposed at the top level in Python 3.7+
* Better SQL support in CocoImage
* Add maxlen in `path_sanitize`
* Warp properties in CocoImage
* Stub out CocoAsset

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