When loading a TapPlan and a resource is missing, it is logged as a Warning rather than Info.

My users commonly copy a TapPlan from one station to another. Oftentimes, one or more resources on the second station has a different name than the first station. They're surprised when the test plan doesn't work correctly, and they report the issue to me. Upon investigation, TAP had logged missing resources as Info, and the user didn't notice this. I think logging it as a Warning will be clearer.

Closes #220 (closed)