metadata: remove obsolete quirks; add sorting and removal of empty values
There used to be lots of quirks that YAML 1.2 has made obsolete. This removes many of those, and refactors that code further. I think it is actually looking pretty rational at this point.
This adds case-insensitive sort for AntiFeatures:: and Categories: and should make it easy to implement the rest of #1105. It also should make fdroid rewritemeta work a lot better for binary repos.
More details in the commit messages, I recommend reviewing commit by commit.
Edited by Hans-Christoph Steiner