- Improve document version page base image cache invalidation on source
  image transformation updates.
- Optimize transformation list generation by replacing several loops with
  list extensions.
- Avoid using the source content transformations when calculating the
  document version transformation list hash. This cause duplicated document
  version page transformation in some cases. Closes GitLab issue #996.
  Thanks to Reinhard Ernst (@reinhardernst

) for the report and debug
  information.
- Improve document version page image API URL hash uniqueness generation.
  Ensure browsers do not use a cached document version page image when
  the transformations of the source object of the version are updated.

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>