Add support for the Ballot operation

[roxaneletourneau]

Is your feature request related to a problem and use case? Please describe.
Ballot is supported on the local-forging package, but not on the high-level APIS.
The ballot operation allows delegates to vote for a proposal using yay, nay or pass during the exploration or promotion phases.

Describe the solution you'd like
We need to add support for the operation on the contract, estimate, batch.

[roxaneletourneau]

Hey team! Please add your planning poker estimate with ZenHub @dsawali @hui-an-yang @zainen