GUI tweaks.

The check_method_timeout() static function was used for processing
timeouts in milliseconds, hence the name.  We are now reusing it to
check arbitrary numbers, so the name is no longer appropriate.

Instead of having checkboxes to enable or disable file rotation
parameters we enable or disable the editboxes where the values are
entered, based on the state of the rotation checkbox.

Similarly, the editboxes for shutdown method timeouts are enabled and
disabled based on the state of the method checkboxes.

The throttle timeout editbox was poorly aligned.