ACCUMULO-4519 patch from Yudong Wu

Adds missing system permission and namespace functionality to the proxy.
diff --git a/src/main/thrift/proxy.thrift b/src/main/thrift/proxy.thrift
index 25510d1..00427c0 100644
--- a/src/main/thrift/proxy.thrift
+++ b/src/main/thrift/proxy.thrift
@@ -131,6 +131,10 @@
   DROP_USER = 5,
   ALTER_USER = 6,
   SYSTEM = 7,
+  CREATE_NAMESPACE = 8,
+  DROP_NAMESPACE = 9,
+  ALTER_NAMESPACE = 10,
+  OBTAIN_DELEGATION_TOKEN = 11,
 }
 
 enum ScanType {