Fix inkscape versioning issue

  * Detect inkscape version of 1.0 rc 1 or later and add some tex to
    call inkscape using new-style command line parameters.

  * Add a preambles loop to the base jinja template so we have an easy
    way to add preamble sections that doesn't require clobbering the
    existing preamble items

  * Add a dump function to pipeline.py so we can dump our output and
    inspect it during debugging.