Update trie using naive approach to support insertion/deletion

[s1na]

verifyMultiproofAndUpdate computes the post state root only for existing but modified accounts. It doesn't support inserting deposits and withdrawals (i.e. inserting new accounts or deleting existing ones).

A big open question is how to efficiently support insertion & deletion in one pass of the turboproof processing. But for now we can apply the naive approach of rebuilding the trie in memory during verification, and later update using the algorithms existing in clients.