Allow a default frame to be set for flipbooks (#3498)
Allow a default frame to be set for flipbooks (#3498)

* Allow for default_frame property on subject

* Fix bug where loops finish on the next frame, not the current frame

* Use 1 as index, not 0

* Add proper handling for default frame subjects

* Check for edge cases for default_frame

amyrebecca/Panoptes-Front-End,amyrebecca/Panoptes-Front-End,jelliotartz/Panoptes-Front-End,jelliotartz/Panoptes-Front-End,amyrebecca/Panoptes-Front-End,jelliotartz/Panoptes-Front-End,zooniverse/Panoptes-Front-End