MyChem query endpoint should return a subset of field by default

[newgene]

Similar to how mygene.info/v3/query behavior. By default, the matching hits return a subset of "essential fields" by default, instead of all available fields. This will return hits much smaller and faster.

Users can always get the specific fields they need by specifying "fields" parameter, or passing fields=all to return all available field (the current default)

[newgene]

Let's define a set of "essential fields" as the default first.

[newgene]

settings example here (from mygene.info):

https://github.com/biothings/mygene.info/blob/master/src/config_web.py#L110

[DylanWelzel]

Google sheet with fields to keep vs drop and example values:
https://docs.google.com/spreadsheets/d/1F1BIZ-hGyzLvBCR5AWU5b9DUxgPGqbomwbb95kRrYCg/edit?usp=sharing