add voting power in VoterInfo of abci

[zemyblue]

Closes: #35

Description

Add voting power in VoterInfo of abci, and fill it when transfer BeginBlock
The Power of Validator is used as staking value when update the validator information and slash evidence.
So, I didn't use it as VotingPower of validator. I add the Power in the VoterInfo structure to transfer a votingpower though.

But later, we need to change the distribution of cosmos-sdk for referencing right voting power.
https://github.com/cosmos/cosmos-sdk/blob/f8df05f6f15e40dc6c4df6ea4246c594769f5f22/x/distribution/abci.go#L20-L23

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For contributor use:

• Wrote tests
• Updated CHANGELOG_PENDING.md
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Updated relevant documentation (docs/) and code comments
• Re-reviewed Files changed in the Github PR explorer

[torao]

This PR only adds Voter.Power to Protocol Buffers, right? (Is the code to use this added Voter.Power going to be fixed later?)

[zemyblue]

This PR only adds Voter.Power to Protocol Buffers, right? (Is the code to use this added Voter.Power going to be fixed later?)

No, this PR add VoteInfo.Power not Voter.Power. And VoterInfo of protobuf doesn't have matched any structure in code, it is just object for transfering vote information of previous block.

Voter.Power is set with Validator.VotingPower when generate RequestBeginBlock for calling BeginBlock.
You can see the code used in https://github.com/line/tendermint/pull/102/files#diff-b92652a6804d4a2173c557bab87194ddR351

[egonspace]

I've looked at various things, and I think it would be better to put StakingPower(it is Power for now) and VotingPower in the Validator in here(https://github.com/line/tendermint/blob/e007be020311ca4ae8cf4b50170b600492ffb509/types/protobuf.go#L74)

Because VotingPower will also be needed to pass Evidence over, it would be better to put it in the Validator.(https://github.com/line/tendermint/blob/e007be020311ca4ae8cf4b50170b600492ffb509/types/protobuf.go#L173)

[zemyblue]

But the Power of Validator should be used as Staking value, because we can take all the staking value of byzantine via evidence when the byzantine's fraud is found. If we use the voting power as Valdiator.Power, we can't get the byzantine's all staking money, because voting power and staking power is difference

And second reasone is that the Validator.Power is used when update valdiator's staking power.

So I think it's better to remain the Validator.Power as staking power.

[egonspace]

I meant to put both StakingPower and VotingPower in the Validator to sync abci.Validator with types.Validator

[zemyblue]

Yes, that's a good point. But as I mentioned above, the abci.Validatoris used three part and there aren't need voting power all part. Voting power is only needed when transfer BeginBlock.
So, I was thinking about what to do. And then I decide to insert voting power to VoterInfo not Validator. Because VoterInfo is only used when transfer voting information in the BeginBlock, so the purpose is equals with voting power. And doesn't used others and doesn't have matched structure.

But as you pointed in offline, the name can make confuse with staking power, hence I'll modify the name more clearly.