ZP-527 document the exact location of the migration script for switching from 2.0 to 2.1

git-svn-id: https://z-push.org/svn/z-push/trunk@1887 b7dd7b3b-3a3c-0410-9da9-bee62a6cc5b5

src/INSTALL

@@ -170,7 +170,7 @@ and re-create profiles on every device.
 
 *Important*
 States of Z-Push 2.0 and Z-Push 2.1 are not compatible. A state migration
-script is available in the tools folder.
+script called migrate-2.0.x-2.1.0.php is available in the tools folder.
 
 Please also observe the published release notes of the new Z-Push version.
 For some releases it is necessary to e.g. resynchronize the mobile.