Refactor persistence library.

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

persistence/implementation/mysql/tests/util/abstract_db_test.e

@@ -0,0 +1,17 @@
+note
+	description: "Summary description for {ABSTRACT_DB_TEST}."
+	date: "$Date$"
+	revision: "$Revision$"
+
+class
+	ABSTRACT_DB_TEST
+
+
+feature -- Database connection
+
+	connection: DATABASE_CONNECTION_MYSQL
+			-- MYSQL database connection
+		once
+			create Result.login_with_schema ("cms_dev", "root", "")
+		end
+end