Create onderstepoortj.csl

The code for Onderstepoort Journal of Veterinary Science. If possible, please could I request that the 'et al' be italicized throughout the code; I just cannot seem to get it right without causing problems!
Update and rename onderstepoortj.csl to onderstepoort-journal-of-veterinary-research.csl

changed locale to en-GB; changed category field to medicine, science and zoology; changed et al to italics; removed font-style="normal"
Merge pull request #979 from burnmeister/patch-5

Create onderstepoortj.csl