Support multi-band raster

[avmey]

Requirements:

• support as input a multi-band raster or a single directory containing single band raster files
• all rasters are setup the same (nodata value, projection, extent)
• generates multi-band raster in output path
• metrics.json must support multi-band. For example can define one top-level datasource, and define a band for each metric group.

See working example here

• Create function to build multiband raster from singleband rasters
• Make sure issues are fixed with geoblaze returning different values for single v multi band rasters (investigate multi-band performance GeoTIFF/geoblaze#226)
• Ensure multiband rasters will run faster than multiple singleband rasters with performance test
• Implement multiband raster building in data:import
• Add multi-band raster support to geoprocessing function and related toolbox functions (rasterOverlap)