Develop test driver base class that manages execution IO

[whart222]

The default behavior in pyutilib.autotest is to call a test driver without worrying what exactly the testdriver does.

In practice, this capability is likely to be used primarily for the execution of external scripts. Consequently, it makes sense to provide a test driver plugin that provides hooks for managing I/O in a standardized manner.

Several other tickets implicitly require this mechanism. This ticket documents the need to develop this generic testdriver.