Add validators for ISNI (c.f. ORCID) and InSet.

Add new validators for ISNI and fixed Sets; fix comment on Date validator.  These validators will be used in SUSHI-Lite, but are generic enough to be global.
I was hoping it would be, but then I ran this on my test VM and got true:
print in_array('B', array(0, 1, 'a', 'b')) ? 'true' : 'false';
So I thought I was documenting backwards functionality.

Must be a local setting in my VM.  I'll research and fix this.