Allow setting "namespace" on lower levels

[niknetniko]

In Bash, we have an exercise where the behaviour of the script depends on its name. In the Bash judge, this is solved by hardlinking the file twice under a different name.

In TESTed, it might be enough to allow setting the namespace on lower levels than test suite level (which is what it currently is). In most languages, this will probably not be that useful (e.g. in Java this used as the class name), but it might for Bash.

See if this introduces problems or not, and if not, if we can add it.

[niknetniko]

This would make things very complex for a rather niche feature.