Emint tx type for eth_call and logs setup

[austinabell]

• Implements new transaction message (EmintMsg) which contains similar data to Ethereum transaction, except V,R,S replaced with a from address since msg will be wrapped in a signed Cosmos stdtx
  • Will be used for eth_call Implement eth_call #38 and sending std txs to use evm as module seperate from Ethermint
  • May need to revisit gas values (or derive based on tx fee since fees are handled by tx) but will be resolved when EVM gas consumption implementation #102 is resolved
• Abstracted state transition logic for consistency between msg types
• Prepared db pre state transition with available data for logs
  • EmintMsg does not (and cannot) have access to tx hash so that will be blank for now
• Indexing tx per block for logs Implement eth_getLogs #55 (don't think a mutex is required since msgs are handled sequentially and couldn't replicate a race condition with many txs)

Edit: Alternative count type to simplify logic I did on seperate branch but let me know if you want me to bring this into this PR for readability: ChainSafe@6396abb

[dutterbutter]

I think rather than a counter:

i := uint(keeper.csdb.TxIndex())

[austinabell]

That's actually the get method that uses the data set in Prepare. I could add two methods to the csdb interface to allow only tx index to be reset and incremented, but would just change the interface/structure of the csdb from mimmicing geth and is only needed within the Keeper/Cosmos.

Let me know if you want me to bring in 6396abb to make the counter more readable/usable or to add those methods to the csdb type

[dutterbutter]

I see. Yeah I would suggest bringing the alternative branch to make it more usable and easier to maintain.

[austinabell]

awesome! just wanted to check before I did because that commit was a bit subjective