[NTG-context] Improved publ-imp-test.bib

Hans, I am using the attached .bib file while working on improving publ-imp-apa.mkvi. The test .bib file contains a short and long version of each publication category, and while it is not an exhaustive test of publications list formatting it is a good start. Perhaps you can consider this to replace the existing publ-imp-test.bib in the core. Robin