Update studia-bas.csl

- bugfix: remove double displaying publisher (book category)
- change: no more displaying "nr" and "t." prefixes when missing number or volume fields (article-journal category)
- change: full date display when "number" field is missing and only year display when "number" field is present (article-journal category)
Update studia-bas.csl

fix for my previous change
Merge pull request #878 from gbalcerowski/patch-2

Update studia-bas.csl