Lost-ds

Added
- Added zip support for pack_ds method

Added
- `bbox_nms` method to directly apply non-max-suppresseion for bboxes
- Argument `path_col` in methods `to_abs` and `to_rel` to enable explicit column specification to look for image paths
- Argument `mode` for method `remap_img_path` to enable not only replacement but also prepending of root paths
- Set argument default of `inplace` of method `pack_ds` to False
- Enable visualization of annos without `anno_lbl` specified

Changes
- `validate_unique_annos` uses data-hash for dropping duplicates now
- `vis_and_store` text-boxes won't be outside the image anymore
- `vis_and_store` can determine optimal text-size for labeling when passing
arg. line_thickness 'auto'.
Added
- dependencies for lost_ds in requirements.txt + setup.py
- examples dataset and code-snippets
- improved function to load datasets at LOSTDataset
- new function `segmentation_to_lost` to convert pixelmaps to lost-annotations
- new function `crop_components` to crop dataset based on annotations
- new function `vis_semantic_segmentation` to color sem-seg. dataset
- new function `to_coco` to generate and store coco datasets from LOSTDataset

Added
- First version