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

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

Files modified:

• web/app/Controllers/StoreController.php
• web/bootstrap/app.php
• web/config.php
• web/resources/views/admin/misc.twig
• web/resources/views/layouts/navbar.twig