ISSUE-219: sh:xor added

I have added sh:xor as decided yesterday:

https://github.com/w3c/data-shapes/commit/b0097b6c0ffd152102464f7d806f5a65f7577ed2

This includes a paragraph trying to explain the difference between our 
sh:xor and the mathematical definition. Input and review welcome.

Thanks,
Holger

Received on Wednesday, 25 January 2017 23:58:59 UTC