Added a common database backend implementation.

Added sqlite (proof of concept)

persistence/implementation/common/database/database_sql_server_encoder.e

@@ -0,0 +1,33 @@
+note
+	description: "Help to encode sql queries, to prevent sql injections."
+	date: "$Date: 2014-08-20 15:21:15 -0300 (mi., 20 ago. 2014) $"
+	revision: "$Revision: 95678 $"
+	EIS: "SQL server injection", "src=http://blogs.msdn.com/b/raulga/archive/2007/01/04/dynamic-sql-sql-injection.aspx", "protocol=url"
+expanded class
+	DATABASE_SQL_SERVER_ENCODER
+
+inherit
+
+	SHARED_LOGGER
+
+feature -- Escape SQL input
+
+	encode (a_string:READABLE_STRING_32): READABLE_STRING_32
+			-- Escape single quote (') and braces ([,]).
+		local
+			l_string: STRING
+		do
+			l_string := a_string.twin
+			if not l_string.is_empty then
+				l_string.replace_substring_all ("[", "[[")
+				l_string.replace_substring_all ("]", "]]")
+				if l_string.index_of ('%'', 1) > 0 then
+					l_string.replace_substring ("[", 1, l_string.index_of ('%'', 1))
+				end
+				if l_string.last_index_of ('%'', l_string.count) > 0 then
+					l_string.replace_substring ("]", l_string.last_index_of ('%'', l_string.count), l_string.count)
+				end
+			end
+			Result := l_string
+		end
+end