scripting the resolver with Velocity "Template" attribute defintion

[Peter Schober]

* Peter Schober <peter.schober at univie.ac.at> [2017-02-14 20:05]:
> The simplest possible test case didn't work:

Because it isn't the simplest, I just realized myself: Just stating
the variable where it's supposed to be set/returned is sufficient.
The following works as expected to prefer $StaffEmail over
$StudentEmail when available:
<Template>#if($StaffEmail)$StaffEmail#else$StudentEmail#end</Template>
-peter