Add WriterSettings to match ParserSettings

There are a number of writer settings that could be supported more easily if they were able to be configured. For example, pretty-printing and other formatting features. In addition, in the case of SPARQL Results XML, we need to be able to add a proprietary feature to markup the documents with q:qname so that they will work with the workbench.

In addition, parser settings should be available for SPARQL Results parsing, so they will be added in this issue.