Fix API Documentation typos

[ranchalp]

(First mentioned in: https://github.com/lightningnetwork/lnd/issues/2180)

Background

the response of openChannel and openChannelSync is not as described.

environment

lnd version 0.5.0-beta commit=a3edcf9cd537ea37a502efc91d262e7017a99e6b
Linux 4.15.0-38-generic #41-Ubuntu 2018 x86_64 x86_64 x86_64 GNU/Linux
btcd version 0.12.0-beta

Steps to reproduce

print "opening channel with bob:"
response = stub.OpenChannelSync(request, metadata=[('macaroon'), macaroon)])
print "response:",response

Expected behaviour

opening channel with bob:
response: { 
    "funding_txid_bytes": <bytes>,
    "funding_txid_str": <string>,
    "output_index": <uint32>,
}

Actual behaviour

opening channel with bob:
response: funding_txid_bytes: "\366\312\323\014\245d\232\313\013\004\001P\245\341<\002\216\017I\203\214j>ub\364~\255\301e\2275"

In fact, only funding_txid_bytes or funding_txid_str can be set at once (set as a oneof as mentioned by roasbeef), and output_index is not set unless different from 0. This should be mentioned in the documentation.

Additionally, there are multiple typos regarding the (recurring) line:

>>> response = stub.NewAddress(request, metadata=[('macaroon'), macaroon)])

There are always mismatching parenthesis when mentioning metadata[...]. This happens accross the documentation. Not a big issue but still one. Should be changed to:

metadata=[('macaroon', macaroon)])

[guggero]

Fixed by #16.