implement sparqlSolutionsWriterSelector for Sesame
remove duplication of code in RDFWriterSelector, use type instead
Merge pull request #201 from read-write-web/issue/200

remove duplication of code in RDFWriterSelector, use type instead
[io] Simplifications.

* no selector
* no Syntax
Merge branch 'topic/io-cleanup' into topic/mutable-graph