Fixed revisions table losing originalIndex when article was deleted

I've also included a migration file in the tools directory

tools/migrations/version-1.3.0.sql

@@ -0,0 +1,6 @@
+use news;
+ALTER TABLE revisions CHANGE COLUMN id `index` INTEGER(11) UNIQUE NOT NULL AUTO_INCREMENT;
+
+ALTER TABLE revisions DROP FOREIGN KEY revisions_ibfk_1;
+
+ALTER TABLE revisions CHANGE COLUMN originalIndex originalIndex INTEGER(11);