Remote Driver integration with Plugin Framework

This commit brings in Remote driver integrated with the newly introduced
Plugin framework as a Docker Package.

The Plugin framework is designed as a Package and has no runtime
dependancy on Docker platform. It stands on its own and is a good
candidate for getting the remote drivers hooked to libnetwork

Signed-off-by: Madhu Venugopal <madhu@docker.com>

driverapi/driverapi.go

@@ -19,6 +19,9 @@ var (
 	ErrNotImplemented = errors.New("The API is not implemented yet")
 )
 
+// NetworkPluginEndpointType represents the Endpoint Type used by Plugin system
+const NetworkPluginEndpointType = "NetworkDriver"
+
 // Driver is an interface that every plugin driver needs to implement.
 type Driver interface {
 	// Push driver specific config to the driver