Support for Occurrence collections (datasets)

[mihow]

Should be able to manually add Occurrences to a list / dataset / collection.

Common use cases:

• Flagged occurrences
• Favorite occurrences
• Save current filtered view to dataset

Similar to collections for Captures

The export feature (#634) will also use this to export a subset of occurrences.
This is a method to save & recall filtered data / queries.

[f-PLT]

Would this actually be part of the Panama features integration? It reads like some of the features that were implemented to switch and/or create new clusters?