Add registrar proxy

[chevdor]

This PR adds a new ProxyType: IdentityJudgement, allowing only Identity.provideJudgement either as single call or batched call.

The main usage is for identity registrars who want to automate their process without exposing the registrar's main account.

Proxy setup:

Usage:

Fix #1290

[bkchr]

LGTM

[gavofyork]

probably worth including utility.batch also.

[chevdor]

yes, that's exactly what I want to add :) I was looking for how to add batch but only a given method.

I have also (not pushed yet) the change for westend and polkadot.

[shawntabrizi]

@chevdor if you directly add Call::Utility(utility::Call::batch(..)) as is done above, the other filters will continue to apply through to the batch call.

[shawntabrizi]

i.e. you will only be able to batch to make the specific calls you have whitelisted. You of course can verify this with a dev node or something.

[chevdor]

This feature can be tested in the UI under settings/dev by adding the following type:

{ "ProxyType": { "_enum": ["Any",
	"NonTransfer",
	"Governance",
	"Staking",
	"IdentityJudgement"
] } }

[chevdor]

No issue here but I am leaving it as draft until I can take a bit more time to test for myself.

[chevdor]

I tested the following on kusama-dev manually:

• Provide judgement as single call thru the proxy - PASS
• Provide judgement as batch call thru the proxy - PASS
• Test proxied transfer from an account with only IdentityJudgement - PASS (All green in the UI but the transfer did not occur)

[chevdor]

Rebased master