Added diagrams and partial code for the building example.

Still need to implement all properties and datatypes (all for energy
and some for location).

Still need to remove the properties and datatypes not used. Don’t know
what to do about the hierarchies, whether to keep only the last class
or the hierarchy (so far the hierarchy is keep only for the branch used)

short circuit voltage changed to object property

prefix is now s4bldg

Added
TTL and RDF/XML files with the provenance information to IFC in
BuildingSmart

Updates in requirements (needed to generate the provenance triples)

Updates in ENVI and BLDG diagrams

First version of the bldg ontology including clases and properties