Lessons Learned: a way to keep the preferred BibTeX provider in Sniffer

[GerHobbelt]

While working on a library recovery project, I found that for this lib (with medical focus) the PubMed search site is far better than Google Scholar for those articles which can be found there: PubMed provides XML including a full abstract and much more metadata than Google Scholar ever has delivered. The remainder could then be grabbed off Scholar.

Hence: I would like a way to save the PREFERRED Search Website (TAB) in Qiqqa Sniffer.

Following the fix of #44, this should maybe become a part of the saved Sniffer Preferences?