Add database upgrading mechanism for adding the audit table.

Signed-off-by: DL6ER <dl6er@dl6er.de>

advanced/Scripts/database_migration/gravity/1_to_2.sql

@@ -0,0 +1,9 @@
+CREATE TABLE audit
+(
+	id INTEGER PRIMARY KEY AUTOINCREMENT,
+	domain TEXT UNIQUE NOT NULL,
+	date_added INTEGER NOT NULL DEFAULT (cast(strftime('%s', 'now') as int)),
+	comment TEXT
+);
+
+UPDATE info SET value = 2 WHERE property = 'version';