[asciidoc] add option to not generate metadata

Created by: man-at-home

add a new cli option (additionalParameter): generateHeaders for asciidoc generator. If set to false suppress generation of attributes in the markup header section.

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@wing328 @jimschubert @cbornet @ackintosh @jmini @etherealjoy

==> please view the boolean command line option, I had to change the type from string to booelan within the generator, otherweise the mustache templates would not work. Are boolean command line options possible?

issue by @mgwoj

For #4848 (closed)