Scenes Bounds Updates

Changed

• scenes.GeoContext: better defaults and bounds_crs parameter
  • bounds are no longer limited to WGS84, but can be expressed in any bounds_crs
  • New Scene.default_ctx uses a Scene's geotrans to more accurately determine a GeoContext that will result in no warping of the original data, better handling sinusoidal and other non-rectilinear coordinate reference systems.
  • Important: the default GeoContexts will now return differently-sized rasters than before!
    They will now be more accurate to the original, unwarped data, but if you were relying on the old defaults, you should now explicitly set the bounds to geometry.bounds,
    bounds_crs to "EPSG:4326", and align_pixels to True.
• Scene.coverage and SceneCollection.filter_coverage accept any geometry-like object, not just a GeoContext.