Added more to the insert preserves proof. We need a lot of lemmas to prove this one
Merge branch 'master' of github.com:nicolaidahl/BPlusTrees
Merge branch 'master' of github.com:nicolaidahl/BPlusTrees
Merge branch 'master' of github.com:nicolaidahl/BPlusTrees
Proved appears_in_kvl_dist_app