improve error-handling when validating

Ticket

+commit
 

Current error message is arcane, and when multi-editing we want to highlight the problem fields.

 

Instead of the current message, something like this:

 

Can't save "hoedads" because:

domain field: 'hi' is not numeric

 

Also, when multi-editing, highlight fields that have a problem (with the arrow below or something similar). Hovering over the arrow would pop up a note such as: domain must be numeric

 

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