Hentai Foundry rip fixes and Y!Gallery ripper

Rolled these two into one pull request as they both edit the same file (DownloadFileThread) for file format fallback support. Brings both rippers up to the ability to rip all the images available from a user or gallery on both sites.

If you can think of a way to do the file format support in a way other than adding it to DownloadFileThread feel free to edit the pull; it seemed to me there was no higher level place to attempt the fallback feature in the ripper itself because those have no access to the observer or the 404 error on the file (and either way it was cleaner without needless error messages for files successfully downloaded in another format.

For HF: Added login to display kink images (default account shows all, gives 300 images per page, and sorts old to new), fixes small bug with usernames starting with a number/symbol, and provides file format fallback (default assumes .jpg, it can be up to 4 file types; this had to be hacked into DownloadFileThread as I couldn't find another place to do the check)

For the new Y!Gallery Ripper: New feature complete ripper with login to display porn images (a default account will need to be provided), image names in the filename (parsed from the same page as image URLs), and subgallery support (both directly linked and nested within base gallery links)