Improve TestingBot support

[occupant23]

You can configure the idle timeout for TestingBot. This can be handy in some cases.

See the following link for details:
https://testingbot.com/support/other/test-options#idletimeout

[jowerner]

TestingBot provides other configuration options that might come in handy, such as maxduration and selenium-version, but there may be more. It might be a good idea to support all currently known TestingBot options, as long as they are simple and can be configured easily in a properties file (i.e. no complex objects).

[occupant23]

added the recommended switches for SauceLabs and TestingBot

[jowerner]

Both SauceLabs and TestingBot document the type of the max-duration and idle-timeout capabilities to be integers. Neodymium, however, pass them as strings. Looks like TestingBot accepts this nevertheless, but this might change. Haven't tried SauceLabs.