Added image showing an RDF Graph.

Taken from W3C:  http://www.w3.org/TR/rdf-primer/fig5may19.png
Added RDF and SPARQL sections.
Added first SPARQL query in DBpedia.
Merge branch 'SPARQL_Lessons'
Added DISTINCT, LIMIT, OFFSET.

With specific examples.
Added song queries.

Examples of ORDER BY clause were added.
Added queries FILTERing by date.
Merge branch 'SPARQL_Lessons'
Added Neo4j queries using Cypher.

Set of exercises used in class.
Merge branch 'Neo4jCypherQueries'
Added examples on label, comma and semicolon.
Merge branch 'SPARQL_Lessons'
Added FILTER, OPTIONAL, MINUS, NOT EXISTS

Example queries were added for each one of these expressions.
Merge branch 'SPARQL_Lessons'