In vertical change pos attribute to tag

[TomazErjavec]

For PoS tagged corpora (no)SkE requires the positional attribute tag.
But ParlaMint has the attributes (UD) "pos" and "feats", so, e.g. trying to compute the frequency of preset "KWIC tags" gives you the error:

Something went wrong…
AttrNotFound (tag) 

For next version "pos" should be changed to "tag". Even though it breaks backward compatibilty.
Or maybe it should even be a patch of 4.0!? It means recompiling all the corpora, but as there is no deadline...

[TomazErjavec]

I guess this stays for 5.1, although it would be introducing backward incompatibility.