Update Teekesselchen.lua

Changed testing for raw to dng (personal more handy)
stripped file base name from file name. If I want to search for full file name I can search on filename and filetype together. (also here it is personal, I do not rename files, only get versions with jpg, psd, tiff etc.)
fixed the bug in the virtual copy detection. Comments are explanatory.

regards,
Michel.


For the dng test and the filename stripping there are probably more elegant solutions (e..g by stripping the last 4 characters of the variable value instead of re-asking LR for the filename).