Allow for setting multiple loglevels at once with logging servlet

Currently when changing loglevels using the logging servlet, when you want to change the loglevel of multiple classes, this needs to be done one by one.

It would be a nice improvement if instead of an apply button per class, there was just one which would then allow you to set the loglevel dropdowns for multiple classes, and then apply. (Or alternatively select a loglevel and choose which classes to apply it to)