This change packages all SVG based icon sets in seperate zip
files. It automatically generates the SVGs links.txt from
the non-SVG version, if it doesn't exists by 's/\.png/\.svg/g'.

Same for the _dark version, but this just copies it.
This would also work for a _dark_svg version, if needed.

The patch explicitly does't package sifr_svg and tango_svg.

Change-Id: I8d7fda42d0ff9a2108ba8406bd4e82af4c54ff0c
Reviewed-on: https://gerrit.libreoffice.org/62706
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>