3.0 update exception

first batch of updates for Exception to start reviewing.

still to be done : add missing exception like MissingElementException, MissingCellException, ...

I'll push an other commit later in the day
This paragraph needs updating. What determines the http status code is the `getCode()` method in the exception. It does not matter what exception class it extends.

It would be worth noting that exceptions extending `HttpException` can have special methods for rendering in the `ExceptionRenderer`.