* sfml: 2.5.0 -> 2.5.1
Semi-automatic update generated by
https://github.com/ryantm/nixpkgs-update tools. This update was made
based on information from
https://repology.org/metapackage/sfml/versions
* sfml: cmake is only needed at build time
Moved cmake from buildInputs to nativeBuildInputs
* sfml: use fetchzip instead of fetchurl
Don't use fetchurl for changing GitHub archive tarballs
* Remove package name
* Start with upper case letter
* Remove trailing period
Also reword some descriptions and move some long descriptions to
longDescription.
I'm not touching generated packages.