[Eevee / 2.8] Explicit control of light probe baking

This seems like something that may already be planned, but I've found no evidence of it, so I'll just put this here for the record because it seems pretty important.

I think the default auto-updating of light probes in Eevee should be disabled and replaced with a manual "bake" button in their properties to rebuild the cubemap/volume. Current development builds seem to rebuild the cache for every light probe when either an object in the scene or the probe itself is moved. This can be convenient, but when you have a large irradiance volume that takes many minutes to update, one change causes the cache to be thrown out and rebuilt, during which time the lighting is missing. This happens frequently if you're making an animation (which involves moving things around a lot).

In addition, a checkbox called "auto update" or similar could be added to enable the currently implemented behavior of instant updates if desired. Also maybe even a control to allow cubemap probes to update for every frame of an animation, since cubemaps can be updated significantly faster than irradiance volumes.