DB/Misc: minor structure improvements

- Affects #https://github.com/azerothcore/azerothcore-wotlk/issues/236

data/sql/updates/pending_db_characters/rev_1478978518254125000.sql

@@ -0,0 +1,5 @@
+INSERT INTO version_db_characters (`sql_rev`) VALUES ('1478978518254125000');
+
+ALTER TABLE `arena_team_member`
+	CHANGE COLUMN `personalRating` `personalRating` SMALLINT(5) NOT NULL DEFAULT '0' AFTER `seasonWins`,
+	DROP COLUMN `personal_rating`;