Added changes for loading entities from triples sparql result, createt m...

Changed SparqlResultDataObjectHelper so now can load sparql query triples -> entities
Changed SparqlQueryContext -> SparqlLinqQueryContext; created new base class SparqlQueryContext to be used for custom queries
Added new context method "ExecuteQueryToResultTypes" that automatically maps triples info to entity types
Added unit tests
Refactored old Context "ExecuteQuery<T>" method code into separate methods.
Added DataObject method to get the entity type for a Uri ("http://.../Person" string -> Person c# type)