Improved usability for new users

I added two error messages in the Marc import page (http://localhost/drupal/admin/content/marc) :

There are not any valid files in the "@marc_file_directory_path" directory
There are not any valid types. You must define them in the content type page, clicking in the marc tab

I want to include a link to the "content type page", but drupal doesn't process html links in the error messages.

The second message it's a little buggy. I try it with

  if (empty($result)) {

and with

  if (empty($types)) {

With The first "if" appear sometimes and others don't but the second one shows the message in every adminpage :(

Patch attached