Add support for FIDO U2F (#3971)

* Add support for U2F

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add vendor library
Add missing translations

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Minor improvements

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add U2F support for Firefox, Chrome (Android) by introducing a custom JS library
Add U2F error handling

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add U2F login page to OAuth

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Move U2F user settings to a separate file

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add unit tests for u2f model
Renamed u2f table name

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Fix problems caused by refactoring

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add U2F documentation

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Remove not needed console.log-s

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add default values to app.ini.sample
Add FIDO U2F to comparison

Signed-off-by: Jonas Franz <info@jonasfranz.software>

docs/content/doc/features/comparison.en-us.md

@@ -535,6 +535,15 @@ _Symbols used in table:_
       <td>✓</td>
       <td>✓</td>
     </tr>
+    <tr>
+      <td>FIDO U2F (2FA)</td>
+      <td>✓</td>
+      <td>✘</td>
+      <td>✓</td>
+      <td>✓</td>
+      <td>✓</td>
+      <td>✓</td>
+    </tr>
     <tr>
       <td>Webhook support</td>
       <td>✓</td>