Whoops debug display

Added Whoops library for better stack trace display. Not available for error mail send because to complicated to implement.
The fallback is ok, I don't like the duplicate code. As you can see, this code:
https://github.com/speakserve/forkcms/blob/72bd439db840e321098afa7c5073ec4cbcbb7493/src/Frontend/Init.php#L214-L216
is identical to this code: 
https://github.com/speakserve/forkcms/blob/72bd439db840e321098afa7c5073ec4cbcbb7493/src/Frontend/Init.php#L219-L221

It's not useful to have the exact same statement after the if else conditional.