instance set names are read incorrectly

When part of an instance, a set (e.g. node set) is written
```
*Nset, nset=bottom, instance=Part-1-1
```
in the input file.
This should be read as a set with name "bottom", but is currently read as "bottom, instance=Part-1-1".
Quick fix would be not not allow comma in the names (need to check if allowed in Abaqus),
but a safer option might be to filter away after the string ", instance=" and anything following it in the key-names.