Show server info page during installation

On the last page of the installer, it would be helpful to show the Drupal server info page. This shows things like PHP version, if Clean Urls are enabled, etc and file permission warnings.

In some instances folks aren't realizing clean urls are disabled when they try and access /admin.

See: #1876804: Is it possible to access the drupal administration?

It might be potentially useful to add a link for the Drupal admin to the Dashboard view (/admin/pushtape) as well, just in case someone gets completely lost.