Rephrase summaries requirement

[m-mohr]

From Gitter:

@fredliporace wrote:

Checking the use of summaries. The spec states "Summaries should summarize all values in every Item underneath the collection, including in any nested sub-Catalogs.". If 'all values' is to be interpreted as a requirement this increases significantly the implementation work. For CBERS case I consider that the only field that would be interesting (and easy) to include in summaries is the GSD for the CB4A/WPM camera, which has assets with 2m and 8m.

My response:

It seems we need a PR to rephrase this.
This was meant to say that for the fields you decide to add to summaries, you should list all potential values from all items underneath for that specific field.

[fredliporace]

@m-mohr I can work on this PR.

[m-mohr]

That would be great, @fredliporace ! Thanks.