Http to https

i'm trying to reduce the amount of cleartext http in the world. this series removes a lot of it from the knot-dns codebase, though some is still left

what remains is mostly in contributed or potentially autogenerated files. in particular, the code copied from Russ Allbery's TAP testing infrastructure has a lot of http:// in its licensing, but upstream he's transitioned it all to https. perhaps refreshing TAP from upstream would be the easiest next step to take.