[osis-core] test19 schema issues

[Harry Plantinga]

I had to make a couple of changes/corrections to the test19 schema to 
make XMetaL happy with it.

1.  Duplicated attributes.
- osisWork is in commonAttributes and inReferenceAttributes
- osisWork is an attribute of osisText, which also has 
    globalAttributes, so that's another duplication
2. maxOccurs="unbound" should be "unbounded" (6 times)

-Harry