SPARQLStore / QE integration

- Add SparqlResultConverter
- Move relevant code to QueryEngine
Doc block tweak
Merge pull request #375 from SemanticMediaWiki/sparql-queryengine

SPARQLStore / QE integration
Fix '#' encoding issue in SMWExporter::findDataItemForExpElement
Update RELEASE-NOTES.md

[skip ci]
Fix for RDF export of Subobjects
Merge pull request #377 from nischayn22/subobject_export_fix

Fix for RDF export of Subobjects
Merge pull request #385 from SemanticMediaWiki/fix-exporter-encoding

Fix '#' encoding issue in SMWExporter::findDataItemForExpElement
Update RELEASE-NOTES.md

[skip ci]
Merge branch 'master' of ssh://wmfgerrit/mediawiki/extensions/SemanticMediaWiki