- Removed PNG icons from /tools/ as they were unused and some already existed in /rtdata/images/
- Removed horizontal.svg and vertical.svg icons from /tools/ as they were unused,
- Moved crossCursor.svg and histogramButtons.svg from /tools/ to /tools/source_icons/
- Ran all PNG files through pngcrush to decrease their size and fix any corruptions (sometimes RT generates a "libpng warning: gamma table being rebuilt", maybe this will fix it)