This function clears the mail queue of all emails, and at the end redirects to browse.

• Requires a valid session ID in the URL
• Finds out how many emails are in the queue if $_GET['te'] isn't set
• Calls ReduceMailQueue() in Sources/ScheduledTasks.php to send 50 emails at a time
• Pauses after each batch of messages is sent to avoid overloading the server
• Redirects to the main mail queue page when done