Refactor persistence library.

Added a persistence speficication cluster and implementation cluser,
Implementation MySQL.
Added test cases for mysql implementation.

persistence/implementation/mysql/tests/nodes/node_test_set.e

@@ -0,0 +1,26 @@
+note
+	description: "[
+		Eiffel tests that can be executed by testing tool.
+	]"
+	author: "EiffelStudio test wizard"
+	date: "$Date$"
+	revision: "$Revision$"
+	testing: "type/manual"
+
+class
+	NODE_TEST_SET
+
+inherit
+	EQA_TEST_SET
+
+feature -- Test routines
+
+	new_test_routine
+			-- New test routine
+		do
+			assert ("not_implemented", False)
+		end
+
+end
+
+