added changelog to database, implemented ON UPDATE RESTRICT

assets/database/README.md

@@ -3,3 +3,7 @@ This is merely a copy of the database.
 In order to use it with the application, it needs to be put in the
 data folder in the application directory, i.e. the folder the application
 is executed in.
+
+# Changelog
+
+When making changes to the database layout, schemas or pragmas make a comment in the changelog table detailing the changes you have made.