Next step is to put more logic into the decision
if Draw or Impress should be loaded - if we have a
self-exported Impress, import as Impress, else
(including all not-self-created SVG Graphics) import
to Draw.
To do this it is necessary to be able to import to
different document formats at all. To do this, add
an internal filter type to the filter mechanism
(types/registration/...) and decide in the SVG
XExtendedFilterDetection::detect from SVGFilter
which one to use.
Added tooling for SVG detection and more, see
SVGFileInfo. This allows to detect for SVG, but
also if the creator was LO and if it was Draw or
Impress. The document format/filter is choosen
accordingly.
Corrected the error with <g visibility="hidden">
Slides inisde <g class="SlideGroup"> for import
of self-exported Impress documents. No idea why
this was written that way, but needs to be fixed
to get a visible content at all.
Also adapted the final mapping from pt to 100thmm
in SvgSvgNode::decomposeSvgNode. Unfortunately
(and also for unknown reasons) the self-exported
Impress does not write svg:width/height values,
thus the adaption from assumed svg-units (px) to
100thmm has to be skipped.
Have identified the place in svgio where I can
embed Pages/Slides to a helper-Primitive to later
be able to 'break' such GraphicObjects to multiple
Pages/Slides. I have added a Primitive called
PageHierarchyPrimitive2D for this purpose.

Change-Id: I38bfef6e7b16479a025fc754e38b4e21a006ad38
Reviewed-on: https://gerrit.libreoffice.org/55434Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>