Fixed SVG warnings on Linux by removing Inkscape/Sodipodi metadata

* Added scripts/clean_svg_files.py utility to strip editor-specific metadata
* Cleaned 46 SVG files (icons, logos, resources) to remove:
  - Inkscape and Sodipodi namespace declarations and attributes
  - sodipodi:namedview blocks
  - RDF/Dublin Core metadata blocks
* Fixes "qt.svg: Invalid path data; path truncated" warnings on Ubuntu
* SVG files now contain only standard SVG elements compatible with Qt renderer

Author: PierreRaybaut