Compare org.opengis.feature package with OGC 17-069

[desruisseaux]

Verify how OGC API - Features - Part 1: Core could apply to the org.opengis.feature package. The OGC API specification seems to be for web API, while GeoAPI uses abstract specifications as its source (in this case, ISO 19109). But we should verify at least that the abstract concepts are similar. In case of overlaps between OGC 17-069 and ISO 19109, I suggest that ISO 19109 should prevail in GeoAPI case. But that would be a question to add in comments below if we find such overlaps.

This issue is related to #32.