Revist field configuration for attribute based layers

[james-rae]

We have a bunch of different config options.

outfields is an optional comma delimited string of field names. If not *, will only include the fields in the list. This impacts the attribute loader. End result affects what is available to display in grid, display in details pane, what's on observables.

fieldMetadata is an array of mappings between field name and alias. Lets author define a custom alias.

The grid config has columns which map to fields. While a bit redundant, I can see the use of having an additional override here if authors want grid to look different / have different column heading.

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Possible idea would be to expand fieldMetadata to include an omit flag, replacing the outfields. I.e. you would have to define fields you don't want instead of defining fields you do want.

Another idea is to push the fieldMetadata array into a property of new field metadata object, and add a boolean property for exclusivity. In this case, if true, we only take fields in the field metadata list. Otherwise the list acts as an enhancer (e.g. you only want to override one alias, only need one element. But if exclusive, need every element).