Metadata uuid from geonetwork

Fixes #1397.

@anguss00 Some thoughts about it:
 * Talk to POs a bit more about it. I had a discussion with @ggalibert
 * Looks like the references in geoserver to geonetwork can stay, but they should not affect portal
 * In terms of AODN, I think it's OK as well, because geonetwork is the point of truth, so if a record is in geonetwork, it will have an abstract/info
 * Possibly some cleanups in the DB side can be done, because we don't need to save the geonetwork URL WMS scanner will give us. @dnahodil, true?
 * Another step forward towards stateless

If it is decided to not use this PR for any reason, the function of `getFormattedMetadata` must be sanitized so it cannot call any random URL. As far as I saw there was no host verification in this function.

The `getFormattedMetadata` refactor is what we should aim for - a clean API which takes parameters on the server side, rather than double or triple encoded URLs that are assembled in JS.
I think it's a good idea to remove ambiguity for these method names. However this metadata is not only used for the GFI popup so that might lead to some confusion later too. Maybe call it layer metadata? so `setLayerMetadata` and `getLayerMetadataUrl`? It's not great, I know, but it might be enough to distinguish from the collection metadata. Thoughts?