always keep RRSIG and its RRset in single data structure
Problem: At the moment RRset and its RRSIG are two independent
This leads to problems like !1072 (merged) where things get mixed and weird things happen after that.
Idea: Refactor code so RRset is always tied to all associated RRSIGs (multiple of them!).
Investigation how this could be done in most efficient way is needed. Maybe this approach could be beneficial also to libknot/Knot DNS so let's not forget to talk to them.