Ember - donation system, bans, loading screen & landing/index page

1. Added session lifetime configuration - remember to add the new configuration option toconfig.php when upgrading
2. Added an optional centered navbar style
3. Fixed a bug with duplicate transaction check

Files modified:

1. web/app/Controllers/StoreController.php
2. web/bootstrap/app.php
3. web/config.php
4. web/resources/views/admin/misc.twig
5. web/resources/views/layouts/navbar.twig