Add support for Sentinel 2 imagery

[nvkelso]

• Get in the footprints catalog
• File format support
• Add to general mosaic

[sethfitz]

https://s2maps.eu/

Bucket details: https://eox.at/2017/03/sentinel-2-cloudless-original-tiles-available/

[sethfitz]

As a first pass, I've added EOX's WMTS endpoint to the catalog (using WMTS:https://tiles.maps.eox.at/wmts/1.0.0/WMTSCapabilities.xml,layer=s2cloudless_3857 as the URL). Longer-term (still this week), we want to use a local mirror of s3://eox-s2maps so it's in the same region (reducing latency) and can be used with GDAL's WMS (TMS) driver w/o needing to work around requester pays issues.

[nvkelso]

We're almost done doing a local copy of Sentinel 2 – once that's done there's a config change to point at those "local" S3 files instead of the WMPS endpoint.