Bug#945588: Reworked for v0.5.5

[Stephan Lachnit <stephanlachnit@protonmail.com>]

I just reworked everything on top of upstream. I upstreamed a lot of stuff I did for 0.5.4-1, so the diff is very small (repo is still the same: https://salsa.debian.org/stephanlachnit-guest/lutris).

I'm still searching for a sponsor, considering the lintian output and the changes compared to upstream the biggest concern is the Flaticon license. More on this topic on the debian-legal mailing list (sadly without any response): https://lists.debian.org/debian-legal/2020/01/msg00020.html

Stephan