Add "White Label" functionality to Status Pages

Allow the Uptime.com branding to be hidden/removed from my public status pages as well as the email notification footer so that users can present a fully white-labeled experience to my users. This feature will add a "Hide Uptime Branding" checkbox under the "Customize Look & Feel" settings page. This functionality will only be available only to Premium and higher-tier plans. When enabled, it will remove "Powered by Uptime.com" from status pages and the footer links to Uptime.com in notifications.