Kwcoco

Added

* Added `vidid` argument to `CocoDataset.images` 1D object mixin.
* Added `trackid` argument to `CocoDataset.annots` 1D object mixin.

Fixed

* `perterb_coco` now correctly perturbs segmentations

Changed

* Changed argument name from `gsize` to `image_size` in toydata methods.
Backwards compatibility is preserved via kwargs for now, but `gsize` will be
deprecated in the future.

Added

* CocoSQLDataset.coerce
* `kwcoco subset` CLI now has a `--select_images` and `--select_videos` option that takes a json query.
* Add initial implementation of `DelayedChannelStack.take_channels`, returns nans if the channel is not available.

Changed

* Made URIs for CocoSQLDataset slightly more robust
* kwcoco show now defaults `show_labels` to False

Added

* Added "domain net" to `kwcoco grab`.
* Added "spacenet7" to `kwcoco grab`.


Fixed
* Fixed issue in `add_annotation` where if failed to add keypoints, and segmentations.

Added

* `CocoDataset.index.trackid_to_aids` is a new index that maps a track-id to
all annotations assigned to that track.

* `kwcoco grab` CLI for downloading and converting standard datasets

* `CocoDataset.delayed_load` now has a limited ability to specify a list of
channels to load, and if it is returned in image or video space.

Changed
* `kwcoco.add_annotation` can now accept and automatically convert kwimage data
structures for segmentation and keypoints.

Fixed
* Channels in a base image can now be None.
* `validate` now prints which field caused the issue

Changes
* Updated README
* Code cleanup
* More docs

Fixes
* Fixed error with empty union
* Fixed error in `delayed_load`

Added

* Experimental `delayed_load` method for an image

Fixed
* Fixed `cats_per_img` in kwcoco stats.
* Fixed `grab_camvid`.
* Fixed legacy `img_root` key not being respected.