Use PRIMARY KEY instead of NOT NULL also in gravity and info tables

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

advanced/Templates/gravity.db.sql

@@ -36,11 +36,11 @@ CREATE TABLE adlists
 );
 CREATE TABLE gravity
 (
-	domain TEXT UNIQUE NOT NULL
+	domain TEXT UNIQUE PRIMARY KEY
 );
 CREATE TABLE info
 (
-	property TEXT NOT NULL,
+	property TEXT PRIMARY KEY,
 	value TEXT NOT NULL
 );