Default value in test config example issue

[UgiR]

In the configuration example:

timeout: 10 # test fails if it does not finish running in 10 seconds (default: None)

While the default Python value for this config setting should be None, the yaml type that correctly resolves to such a value is null, and should therefore be listed as such in the documentation.

A yaml type of None will resolve to a Python string 'None'.