Support sending tokens on contract-contract calls

[ethanfrey]

Summary

This was noted as a TODO in the code: https://github.com/cosmwasm/wasmd/blob/29f1c3cccfd83d3a6251bb07e337ee9bd3cbb882/x/wasm/internal/keeper/keeper.go#L311-L313

Problem Definition

Cosmwasm lets contracts send coins to other contracts. If the runtime doesn't support this, we may produce undefined behavior in the contracts that use this.

Proposal

Parse this field as well, and make the proper transfers

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[ethanfrey]

Note: this has been updated in go-cosmwasm just not wasmd