Return the whole presetRef when listing observations

[tomasciccola]

Description

Currently when listing observations through the web API we return associated tags with that observation. Some presets (categories) don't have tags which means a hard to categorize observation. Ideally, observations returned by the API should include the presetRef resolved (so, not returning the id, but the whole preset doc).
A thing to decide is if the preset itself resolves its references, since a preset has fieldRef and iconRef.
It would be useful as a first feature (if its possible) to just resolve the fieldRef, iconRef doesn't seem a priority at a glance.
If the complexity of solving this is big, a compromise would be to just return the name of the preset

[gmaclennan]

FYI presets/categories should always have tags, and each preset/categories tags should be different. We need to enforce that when building presets and/or reading presets. It's necessary for exploring / filtering and exporting data in the future.