Add support for v0.11 GRPC services

This also refactors the client GRPC wrapper to dynamically load the
request objects.
All GRPC generated client files now live under lib/grpc_services

lnrpc.gemspec

@@ -23,7 +23,7 @@ Gem::Specification.new do |spec|
   end
   spec.bindir        = "exe"
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
-  spec.require_paths = ["lib"]
+  spec.require_paths = ["lib", "lib/grpc_services"]
 
   spec.add_development_dependency "bundler", "~> 1.17"
   spec.add_development_dependency "rake", "~> 13.0"