Don't pass MessageInfo to migrate

[ethanfrey]

Follow up from #674 (comment)

We currently do not allow sending funds in the migrate command in wasmd, and the sender is meaningless, as this is a permissioned call, so we never need to check it anyway.

I propose to simplify this and use the same function signature as query. In fact, other "priviledged" calls, like handling ibc messages, also likely do not need this field.

---

• Implementation (Remove MessageInfo argument from migrate entry point #709)
• CHANGELOG+MIGRATING entry

[webmaster128]

Interesting. This means it is completly up to the chain to decide who has permission to migrate. And there can be permissioning schemes that work different than the admin field we came up with.

[webmaster128]

For everything the MessageInfo::sender was used for, we can also use the migrate message, like here:

pub struct MigrateMsg {
    pub payout: HumanAddr,
}

[webmaster128]

@venkattejaRaavi it seems like I cannot assign you here. But feel free to give this ticket a try. Let me know when something is unclear.

[webmaster128]

Re-opening since this really needs a proper CHANGELOG and MIGRATING entry. But I can do that.