R4R: TX Routing Refactor

[alexanderbez]

Redesign the way Ethereum transactions are handled by treating them as first class citizen types along with any potential future SDK messages types by using the Amino encoding protocol. Web3 compatibility is still maintained as Ethereum transactions will still be RLP encoded over the wire but to Tendermint, they'll be re-encoded via Amino.

Changes:

• Refactor Transaction to be a sdk.Msg
• Update ante handler to reflect Transaction changes
• Update ante handler unit tests
• Add crypto utils
• Update tx doc

Note: The ante handler is practically identical to the Cosmos SDK ante handler atm.

closes: #492

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• [x] Wrote tests

• [ ] Updated relevant documentation (docs/)

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• [x] rereviewed Files changed in the github PR explorer

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[alexanderbez]

I believe most of the routing logic is done. Just need to update (re-implement) the ante handler unit tests.

[cwgoes]

I'd like to review this but it's a bit lower priority than GoS.

If you can wait a day or two @alexanderbez I promise to get to it :wink:.

[alexanderbez]

No rush @cwgoes -- take your time.

[alexanderbez]

@cwgoes I believe I addressed most of your comments 👍