Clean all SVG icons: remove Inkscape metadata and fix conflicting fill/stroke attributes

- Removed Inkscape/Sodipodi namespaces and metadata from 243 SVG files
- Fixed conflicting fill/stroke attributes (removed when in conflict with style)
- Converted style attributes to presentation attributes for better Qt compatibility
- Added clean_svg_icons.py script for automated SVG cleaning
- Improves rendering consistency between Qt and Windows native renderers

Author: PierreRaybaut