Announcing start of DNF 5 development

DNF, the Fedora package manager, is going to be significantly rewritten; itseems it is truly "development not finished" for now."We've managed to drop a lot of redundant code across the whole DNF stack in the past years, but we have reached a point when it's nearly impossible to consolidate the code any further without breaking the API/ABI. Especially with PackageKit being dead, we can't move with the old 'libhif' API in libdnf, because making any bigger changes to PackageKit is clearly out of scope."