Use log4js with captured browser output logs.

### Expected behaviour
I was surprised today that the captured browser output didn't use log4js logging or configured loggers. It would be nice if the captured browser logging used the same loggers configuration as configured with karma, or if it has it's own configuration options under browser capture options. This was mostly needed as I was attempting to color the logging output from the browser.

### Actual behaviour
The captured browser logging doesn't use log4js