Added readme for SAREF4AGRI

Include main classes and properties  in the diagram for the “Use case
2: Smart irrigation”.

Include main classes and properties for the “Use case 2: Smart
irrigation”.

adding diagram in the readme

OnToology update

test read in a inner folder

added diagram and owl code for s4agri first working draft

added saref:hasDescription only rdfs:Literal as local restriction

update HTML for revision version and overall diagram

OnToology update

Removed s4city:Measurement.
Removed skos:Concept generalising the solution to broader options.

Updated diagram according to @rgcmme updates

Replaced KeyPerformanceIndicatorValue y KeyPerformanceIndicatorAssessment, since "Value" is misleading.