Suggestion: Custom cdART

Along the lines of the custom banners that were introduced last month, I thought I'd try something similar for cdARTs, even for TV shows. It works for the 5 viewtypes that utilize cdART (List, LowList, InfoPanel, Shift, Showcase), and I've added an option to disable them if they're not wanted. I tried to keep it simple, just the logo and the studio icon overlayed on top of a fanart covered disc. The CD icon I used (common/cdart/custom.png) had to look that way (inside a 16:9 frame) so that I could use 'aspectratio=keep' without problems, because even though 'scale' works, it makes the discs appear elongated in non-16:9 screens. The only issue I've been having is with the rare cases of non-16:9 fanarts that look a bit deformed due to 'keep'.

Anyway, check it out and feel free to throw it out if you don't like it. Thanks.


EDIT: There were some stuff I had neglected originally, that's why there are additional commits. If necessary, I could close this PR and make a new one with only one commit.