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

• Fixed an issue that caused error 400 (bad request) in some cases
• Disabled revoking CAMI groups when there's no Ember group set for the time being

Files modified:

• web/app/Controllers/ServerApiController.php
• lua/ember/lua/ember/init.lua
• lua/ember/lua/ember/store.lua