[ONOS-5884]YANG Serializer: Implement XML serializer.

Change-Id: Idffda88938d9c6c7b7c7814127a340bd2dc35039
diff --git a/serializers/xml/src/test/resources/testModuleLevelLeaf.xml b/serializers/xml/src/test/resources/testModuleLevelLeaf.xml
new file mode 100644
index 0000000..13da6e6
--- /dev/null
+++ b/serializers/xml/src/test/resources/testModuleLevelLeaf.xml
@@ -0,0 +1,2 @@
+<bool xmlns="yrt:food">true</bool>
+<boolean xmlns="yrt:food">true</boolean>
\ No newline at end of file