Added a common database backend implementation.

Added sqlite (proof of concept)

persistence/implementation/common/database/database_connection_null.e

@@ -0,0 +1,67 @@
+note
+	description: "Null object to meet Void Safe."
+	date: "$Date: 2014-08-20 15:21:15 -0300 (mi., 20 ago. 2014) $"
+	revision: "$Revision: 95678 $"
+
+class
+	DATABASE_CONNECTION_NULL
+
+inherit
+
+	DATABASE_CONNECTION
+		redefine
+			db_application,
+			is_connected
+		end
+
+create
+	make, make_common, make_basic
+
+feature -- Initialization
+
+	make_common
+			-- Create a database handler for ODBC with common settings.
+		do
+			create db_application.login (username, password)
+			db_application.set_hostname (hostname)
+			db_application.set_data_source (database_name)
+			db_application.set_base
+			create db_control.make
+		end
+
+	make (a_username: STRING; a_password: STRING; a_hostname: STRING; a_database_name: STRING; connection: BOOLEAN)
+
+			-- Create a database handler for ODBC.
+		do
+			make_common
+		end
+
+	make_basic (a_database_name: STRING)
+
+			-- Create a database handler for ODBC.
+		do
+			make_common
+		end
+
+
+	login_with_connection_string (a_string: STRING)
+			-- Login with `a_connection_string'
+			-- and immediately connect to database.
+		do
+			make_common
+		end
+
+
+feature -- Databse Connection
+
+	db_application: DATABASE_APPL[DATABASE_NULL]
+			-- Database application.
+
+
+	is_connected: BOOLEAN
+			-- True if connected to the database.
+		do
+			Result := True
+		end
+
+end