Image-dataset-converter-imgaug

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- added support for placeholers: `idc-combine-sub-images`

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- `idc-generate-regions` tool can take margins and overlaps (right/bottom) into account for its region calculations now
- `idc-combine-sub-images` tool now has more details in the exceptions when extraction of groups fail
and prunes the annotation after the merge as well
- `meta-sub-images` now outputs a logging message if there are no annotations after transferring
regions/pruning annotations
- method `transfer_region` now adds the sub-images rather than replacing the tile in the overall layer,
to allow for overlaps (for reducing edge effects)

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- requiring image_dataset_converter>=0.0.5 now

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- switched to underscores in project name
- switched to new methods from idc.api: `empty_image(...)` and `array_to_image(...)`

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- switched from unmaintained imgaug to imgaug3 library (https://github.com/nsetzer/imgaug)

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- added `find-contours` filter for turning blobs in image segmentation annotations into object detection polygons.