Updated the admin interface

Mostly updated the admin interface, also some small other items.

- Added more diagnostic information to (hopefully) decrease issue
  reporting, or at least solve them quicker.
- Added an option to generate a support string which can be used to
  copy/paste on the forum or during the creation of an issue. It will
try to hide the sensitive information automatically.
- Changed the `Created At` and `Last Active` info to be in a column and
  able to sort them in the users overview.
- Some small layout changes.
- Updated javascript and css files to the latest versions available.
- Decreased the png file sizes using `oxipng`
- Updated target='_blank' links to have rel='noreferrer' to prevent
  javascript window.opener modifications.

src/static/templates/admin/login.hbs

@@ -1,4 +1,4 @@
-<main class="container">
+<main class="container-xl">
     {{#if error}}
     <div class="align-items-center p-3 mb-3 text-white-50 bg-warning rounded shadow">
         <div>