NABat Export Annotations

[BryonLewis]

resolves #161
resolves #74

Creates some exporting functionality for annotation

• Ability to export NABat Annotations
• Created ExportedAnnotationFile as a new model that is created when exporting data. The idea is that in the future we can use this file for BatAI exporting as well.
• New /export-annotation routes to get the files or the status of an export-task.
• Process is that a filter is provided for exporting, a celery task is created that generates a JSON file and a CSV file of the exported annotations and places them inside of an ExportAnnotationFile Model
• The filter is designed that in the future you can export multiple NABat Recordings at once instead of the current way of doing it one at a time.
• The ExportAnnotationFile and some of the code for exporting is meant to be re-used when we implement this for the base BatsAI version as well.
• The main way to interact with this is to load sample data for NABat and then inside of the NABat interface, look at recordings and click on the export button.