Solved 'n0 < witness1' in the overflow-case of leafs. One less admit.
Proved the child-overflowed-but-fit-in-parent cases for leaf in insert'_impl_appears.
insert'_impl_appears no longer has any admits. Now lets try and pull and see if it breaks
Merge branch 'master' of github.com:nicolaidahl/BPlusTrees
Adjusted insert'_impl_appears proofs to the new assumptions for the greater-key lemma.
Merge branch 'master' of github.com:nicolaidahl/BPlusTrees