New feature: Partial sequence deletion in Mapillary web frontend

Background

• As an contributor, I typically try to upload GoPro timelapse videos.
• After data ingestion, I typically inspect the imagery in the Mapillary web frontend.
• When a complete video is uploaded it can happen that unnecessray images are logged, e.g. maneuvering on a parking lot or video logging while taking a break.
• In such cases the web frontend offers to delete individual images which can be a tedious procedure. Deleteing the whoel sequence is available today but would also drop the portions of the sequence that should be retained.
  It would be helpful to have more granular options to delete portions of the sequence.

New feature proporsal

1. The Mapillary webfront end should provide an option to delete all the images of a sequence from the current image until the end of the sequence.
2. The Mapillary webfront end should provide an option to delete all the images of a sequence from the beginning of the sequence to the current image.

The issue names no files, tests, or implementation entry point, and this repository is described as command-line tools. First locate the Mapillary web frontend and its sequence-deletion flow, then confirm whether this repository contains the relevant code. Done means supporting deletion from the current image to either sequence boundary without deleting the retained portion.