changed pnd and southbound interface

- added function to create a pnd and a interface
- pnd contains a slice of southbound interfaces
- southbound interface contains a slice of clients

nucleus/principalNetworkDomain.go

 package nucleus
 
+import "code.fbi.h-da.de/cocsn/gosdn/nucleus/interfaces"
+
 type pndImplementation struct {
+	name         string
+	sbiContainer []interfaces.SouthboundInterface
+}
+
+//NewPNDImplementation creates a Principle Network Domain
+func NewPNDImplementation(name string, sbi ...interfaces.SouthboundInterface) interfaces.PrincipalNetworkDomain {
+	return &pndImplementation{
+		name:         name,
+		sbiContainer: sbi,
+	}
 }
 
 // Interface satisfaction

sbi/restconf/southboundInterface.go

 package restconf
 
+import "code.fbi.h-da.de/cocsn/gosdn/nucleus/interfaces"
+
 type southboundInterface struct {
+	name            string
+	clientContainer []interfaces.Client
+}
+
+//NewSouthboundInterface creates a Southbound Interface
+func NewSouthboundInterface(name string, clients ...interfaces.Client) interfaces.SouthboundInterface {
+	return &southboundInterface{
+		name:            name,
+		clientContainer: clients,
+	}
 }
 
 // Interface satisfaction
@@ -16,7 +28,7 @@ func (sbi *southboundInterface) CollectHeartbeats() error {
 	return collectHeartbeats()
 }
 
-func (sbi *southboundInterface) ListClients() error {
+func (sbi *southboundInterface) ListClients() map[int]interfaces.Client {
 	return listClients()
 }
 
@@ -34,6 +46,6 @@ func collectHeartbeats() error {
 	return nil
 }
 
-func listClients() error {
+func listClients() map[int]interfaces.Client {
 	return nil
 }