update browsing mode with new icons

[dendrodan]

Since browsing mode has a different use set, we should update the icons in a way that improves user perception of dating without overcrowding the visible ring area.

• Smaller points that are on by default, something basic not needing the precision of the reticle.
• Different icons/colors? for centuries and mid centuries.
• ?

If we bake this feature set up nice, perhaps we could add it as a layer available to enable in popout/measurement mode.