StacLayerRasterSource implementation

[pomadchin]

StacLayerRasterSource implementation with can be built on top of the MosaicRasterSource but with its metadata populated from the StacLayer endpoint. This is a working name, this task also includes investigation of what needs to be done and investigation of the ideal metadata response. This RasterSource should be able to work in case there is not StacLayer metadata or this metadata is partially missing.

With this feature GeoTrellis Server no longer needs STAC Layer supported time range specified in it's configuration.