External direct deposits v1

[kilrau]

Is your feature request related to a problem? Please describe.
As discussed, we would want to have predecessor of #1166 to enable external direct deposits from a UX perspective (even though under the hood there are still 2 steps and 2 on-chain transactions).

Describe the solution you'd like

1. connext client returns 0x address
2. user deposits to 0x address
3. connext client sends meta transaction to node
4. node executes this second transaction on user's behalf

Describe alternatives you've considered
N/A

Additional context
N/A

[ArjunBhuptani]

Will work on setting this up this week

[kilrau]

Dope!

[ArjunBhuptani]

Closing this -- as per our discussion a few weeks back, this is sadly not possible without requiring more upfront work from the user