v0.26.0

This release adds additional APIs on the Reader:

• get_active_manifest, returns the active manifest (parsed as a dictionary for easy use);
• get_manifest, retrieves any manifest based on its label/id and returns it as dictionary;
• get_validation_state, returns just the validation state of the whole manifest store;
• get_validation_results returns all the validation results from the manifest store (and only the validation results).