EVM Transaction handler and contract creation

[austinabell]

• Updates CLI command to have optional to address to allow for contract creation
• Fixes account encoding and decoding from implicit static codec reference
• Updates Ethermint errors
• Implements state transition function/ Handler logic to process Ethereum msgs/txs

Will put up as a draft PR since gas isn't actually consumed from the account and validators are not rewarded, but we can merge it in and create an issue to update when the functionality is decided on if wanted. (Would be nice to get this in to be able to test RPC calls)

To run:

make install 
rm -rf ~/.emint*
emintd init moniker --chain-id 3
emintcli config chain-id 3
emintcli config output json
emintcli config indent true
emintcli config trust-node true
emintcli keys add austin
testpass
testpass
emintcli emintkeys add austineth
testpass
testpass
emintd add-genesis-account $(emintcli keys show austin -a) 1000photon,100000000stake
emintd add-genesis-account $(emintcli emintkeys show austineth -a) 100000000photon,100000000stake
emintd gentx --name austin
testpass
emintd collect-gentxs
emintd validate-genesis
emintd start --pruning=nothing --rpc.unsafe

To send a transaction:

emintcli tx ethermint generate-eth-tx 5photon 22011 6 test 756F45E3FA69347A9A973A725E3C98bC4db0b5a0 --from austineth

Contract creation:

emintcli tx ethermint generate-eth-tx 5photon 22011 6 test --from austineth