Remember render by attribute thresholds when multiple models chosen

[Willow.Coyote-Maestas@…]

Render by attribute remembers the thresholds and colors last used for a single structure and an attribute. But if multiple models are chosen in the render by attribute panel then it does not remember the thresholds. Would be helpful if it remembered the thresholds for each model in the multi-model case.

This is useful for coloring different structure conformations (e.g. open vs closed) switching between different deep mutational scan scores.

If you choose multiple models then the remembered thresholds for the models may conflict with each other. Only set the histogram thresholds and colors if all the chosen models do not have conflicting remembered thresholds and colors.

[pett]

Now fixed AFAICT. Fix available in next daily build.

Fix: ​https://github.com/RBVI/ChimeraX/commit/53ae06726fcf773fea43e7c6691da96f3c39ba5b