add into test context information about stderr output

There will be information about file with stderr-output from jpylyzer.

I thing the file does not exist yet.
I it does not exist yet, please, create it by calling jpylyzer on a proper image.

And reference to this file will be as next line in a test context file:

https://github.com/Differ-GSOC/differ/blob/master/differ-cmdline/src/main/resources/appCtx-differ-tests.xml#L21

:+1: 

Jan
