Windows zip format support

This release fixes:

• Don't display images for projects when the don't exist
• Extract zip files with '' as path sepparator (windows)

docker run \
  --detach \
  --volume /path/to/doc:/var/docat/doc/ \
  --volume /path/to/locations:/etc/nginx/locations.d/ \
  --publish 8000:80 \
  randombenj/docat:0.0.7