For T7435, this...
- Adds a resource folder named preset_icon, which contains tool_icons and emblem_icons. These are filled with pngs.
- Adds a little dialog for loading and combining the above pngs into a preset icon, with some sliders to adjust the look of the tool icon.
Things that need to be considered:
- Do we want to create the folders for the icons in the user's resource directory too?
- Maybe the grid for the tool icons should just have two side by side...
- The last slider is actually a super-simple levels filter, how should we go about naming it properly?