Don’t show system properties with __ prefix in select one from map bottom sheet

[lognaturel]

Currently, the select one from map bottom sheet shows all Entity properties, including system properties like __branchId. Let’s filter out all properties with the double underscore prefix since they are not useful to users.

Currently all data sources for a select one from map are treated the same. I think we can continue that and always filter out properties with the prefix regardless of whether we’re dealing with choices from a repeat, an internal list, an Entity List, etc.

[seadowg]

Do we explicitly reserve property names with __ for all secondary instances? I know we do this for entities, but I'd worry that this could hide data for people not using entities.