GH-5852 Added support for directive serialization style in turtle wri…

[ivairali]

…ters

GitHub issue resolved: #5852

Briefly describe the changes proposed in this PR:

Added a Turtle writer setting to configure the directive style.

Setting the USE_SPARQL_STYLE_DIRECTIVES corresponds to using: VERSION, PREFIX, BASE and no terminating dot '.'. By default the property is set to False and the corresponding style is: @version, @prefix, @base where the statement is terminated by a dot.

The affected writers are Turtle, Trig and N3.

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PR Author Checklist (see the contributor guidelines for more details):

• [ v] my pull request is self-contained
• [v ] I've added tests for the changes I made
• [v ] I've applied code formatting (you can use mvn process-resources to format from the command line)
• [ v] I've squashed my commits where necessary
• [v ] every commit message starts with the issue number (GH-xxxx) followed by a meaningful description of the change

[hmottestad]

@ivairali is this complete and ready to merge?