watchtowerrpc: format watchtower.proto and remove json_name fields
watchtowerrpc: format watchtower.proto and remove json_name fields

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.

aakselrod/lnd,LightningNetwork/lnd,LightningNetwork/lnd,aakselrod/lnd