Link to "external tools package" page on the web site is incorrect

There is a link "external tools package" on the "External tools" page of the UGENE Application Settings. In the current UGENE version 1.31 it refers to http://ugene.net/external.html. However, the web site structure has been changed. So, an error is shown in a web browser:

404: Page not found

Fix the issue as follows:

1. Modify the "download-all.html" page on the web site, so that it is possible to refer to the "External Tools Packages" section on the page.
2. Modify the link in the Application Settings to this section (and also improve the text).
3. Create "external.html" page on the web site and add redirection to the "External Tools Packages" section of the "download-all.html" page. In this case users that have old UGENE versions will be led to the right location.
4. Create a GUI test that copies the link location in the Application Settings and checks that the opened html page doesn't contain message (case insensitive):

   not found