eth: add ResetWithGenesisBlock
eth: add ResetWithGenesisBlock

This depends on a change in ethash which exposes UpdateCache.

maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum