issue-121 ssn:sensordatasheet

Ssn:SensorDatasheet got stranded by the removal of dul.   I have done a quick web search for its use and although there are plenty of  ontology extensions or copies,   code, and explanations (presentations, papers)  that use Ssn:SensorDatasheet --- it appears to me that they are generally only using it because it exists - not necessarily because it is useful or that they have instantiated it.

This ontology as a counterexample seems to  deliberately depend on it http://bci.pet.cs.nctu.edu.tw/ontology/linked_data_engine.jsp?URI=http%3A%2F%2Fbci.pet.cs.nctu.edu.tw%2Fontology%23&SEARCH=%3Fprevious-version%3DBCI-v0.9.9.owl&HASH=

So perhaps it could be deprecated (but not removed) just because it is not used much? On the other hand,  perhaps it needs more filling-out to become useful.

Btw - if we are keeping it,  I note typo in comment to be fixed: "manufacturers".

-Kerry