Pattern preventing Pset_

[atomczak]

Originating from github.com/buildingSMART/IDS/issues/241.

The pattern .* on property set raises an error, because it might as well be 'Pset_'. I tried changing the pattern to Ps.* and it still triggers an error, but Psx.* already passes the audit. I am not sure how the Audit tool achieved this sophisticated precision (well done!), but I think it's better to be less conservative and not raise errors in such cases.