added validation of application names to prevent conflicts at a later

stage with genrated resource names.

The Server resource names will use the -pNNNN suffix to indicates a
linkerd Server resource for port NNNN

example/config.yaml

@@ -16,6 +16,9 @@ namespaces:
   - name: openns
     open: true
     applications:
+      - name: myapp
+        matchLabels:
+          app: myapp
       - name: openapp
         ports:
           - port: 100