Wallet CLI commands

[austinabell]

Task summary

dependent on #465 and just provides a CLI interface for the functionality exposed over rpc

commands options reference (from lotus):
new Generate a new key of the given type
list List wallet address
balance Get account balance
export export keys
import import keys
default Get default wallet address
set-default Set default wallet address

Specification reference

Other information and links

[amerameen]

On hold for now, since we don't have HTTP support, and we are focused on interop. Will come back to this after interop.

[connormullett]

Update: 7/11 commands working. Import, export, sign, verify are still WIP