Rewrote Ingest to use Geotrellis warp/crop 

In the geotrellis-spark Ingest code, geotools resampling was problematic on multiple fronts: an occasional tile being larger than expected (so bad data) and > 1s per tile resampling (poor performance). Replaced geotools resampling with geotrellis warp/crop and solved both the above problems. 

Also, replaced the concept of Bounds with Extent in geotrellis-spark.