Gallery-dl

- Added new extractors:
- pinterest
- rule34
- dynastyscans
- imagebam, coreimg, imgcandy, imgtrex
- Added login capabilities for batoto
- Added `--version` cmdline argument to print the current program version and exit
- Added `--list-extractors` cmdline argument to print names of all extractor classes together with descriptions and example URLs
- Added proper error messages if an image/user does not exist
- Added unittests for every extractor

- Added new extractors:
- luscious
- doujinmode
- hentaibox
- seiga
- imagefap
- Changed error output to use stderr instead of stdout
- Fixed broken pipes causing an exception-dump by catching BrokenPipeErrors

- New modules (imagetwist, turboimagehost)
- Manga-extractors: Download entire manga and not just single chapters
- Generic extractor (provisional)
- Better and configurable console output
- Windows support