Escape n3 triples to deal with multiline issues

[joshmoore]

@andrawaag has been running into issues with various parsers due to the newlines in literals:

http://www.openmicroscopy.org/rdf/2016-06/ome_core/Value      """<SegmentDefinition>
          <Name>example</Name>
          ...
        </SegmentDefinition>""" .

Based on:

• https://stackoverflow.com/questions/15392730/in-python-is-it-possible-to-escape-newline-characters-when-printing-a-string
• https://stackoverflow.com/questions/74643162/python-rdflib-string-to-uriref-or-literal-inverse-of-n3-method produces strings with embedded \n escapes:

<http://www.openmicroscopy.org/rdf/2016-06/ome_core/Value>      """<ChannelThresholds>\n          <RoiName>012</RoiName>\n 

If this is not sufficient, then we may need to create a Graph object very frequently and use the .serialize() method.