Cleaned the stuff related to stores and SPARQL.

* got rid of the Free[Command]
* RDFStore is now a typeclass
* it is made of 3 three independent ones: GraphStore, SparqlEngine,
  Transactor
* there is an additional Lifecycle typeclass for start/stop operations
  * it comes with a default instance doing nothing
* syntax enhancement are made available from within the typeclass themselves
Updated banana-sesame and examples with the changes in the typeclasses.
Merge branch 'master' into topic/rdfstore-typeclass-cleaning

Conflicts:
	jena/src/main/scala/jena/JenaStore.scala
	rdf-test-suite/src/main/scala/GraphStoreTest.scala
	rdf/src/main/scala/Command.scala
	rdf/src/main/scala/SparqlEngine.scala
Merge pull request #114 from w3c/topic/rdfstore-typeclass-cleaning

Some improvements to come in the next mergers