Add object detection

Adds an object detection task by absorbing data and models from biosignal/software/deepdetect>.

Missing items:

• Ensures prediction for detection tasks works
• Implement evaluation for detection tasks, with specific metrics if need be
• Implement support for chexphoto (annotations on @mrenzo account?)
• Implement test units for the CLI, and databases at least
• Implement test units for object detection evaluation
• Update documentation details