Napari-feature-classifier

Refactored the annotation workflow to be separate from the classifier

The new annotator can be used standalone
The annotator uses the layer.features table to store annotations
The new annotator is not yet integrated into the classifier workflow

Initial release of the napari-feature-classifier plugin

- Users can create interactive classifiers, add annotations within napari and interactively train it
- Supports multiple images used for training the classifier
- Contains export functionality of both user annotations and classifier predictions