[Feature] Achievements

[Simbax]

I think achievements are worthless without the SteamWorks API or any other platform-specific reward system like XBox Live or Google Play Services. Since they are impossible to work with in open source projects due to licensing issues, I see no need for achievements whatsoever unless we build our own server infrastructure and force users to create accounts and synchronize their profiles online, which is not only not achievable for us, but also not a good idea at all.