Create spec for OPT1.4

We only have XSD as documentation for OPT1.4

It would be useful for communication to have a document with an UML diagram + some description of the structure with some sample mappings from ADL to OPT (optional).

Add an OPT item in the specs page http://www.openehr.org/programs/specification/workingbaseline

Also add the XSD for OPTs: https://github.com/ppazos/cabolabs-ehrserver/blob/master/xsd/OperationalTemplate.xsd