Transform SatelliteImage class into an optional dictionary attribute in Raster

[rhugonnet]

After more thinking, the organization Raster / SatelliteImage / DEM does not make so much sense anymore: some DEMs can be purely modelled, and are not necessarily from an acquisition.

In the end, the SatelliteImage class is essentially just an extra metadata parser on top of Raster, which could live as simply an __init__ option of the Raster class and store the metadata in an optional dictionary attribute such as the tags attribute for raster metadata.

In short, we could:

• Remove the SatelliteImage class,
• Add the functionalities as a parse_sensor_metadata option to Raster, true by default, which stores all in a .sensor dictionary attribute,
• Subclass DEM from Raster.

[adehecq]

Good idea !!