We now use the jsonpb marshaler to convert the RPC responses to
JSON in lncli and REST. The jsonpb has a setting to use the
original name as defined in the proto file and the explicit
json_name definition is not necessary any more.
The jsonpb setting is called OrigName and needs to be true.
This commit adds a new service lnrpc/autopilot, that is to be used to
communicate with the running autopilot. Currently a RPC for getting the
status of the agent is included, as well as enabling/disabling at
runtime.
