Log Message:
gallery-dl: Update net/gallery-dl to 1.5.1

Changes:
1.5.1
-----
- Added support for:
   * `piczel` - https://piczel.tv/
- Added support for related pins on `pinterest`
- Fixed accessing "offensive" galleries on `exhentai` (#97)
- Fixed extraction issues for `mangadex`, `komikcast` and `behance`
- Removed original-image functionality from `tumblr`, since "raw"
  images are no longer accessible