Potential improvements to get_data

[maximlt]

Just listing here some ideas I've got after using the method when doing eodag's documentation.

• [x] Make the parameters crs, resolution and extent optional
• [ ] Add progress_call optional parameter to pass it down to path_of_downloaded_file = self.download()
• [x] Document the fact that the data is resampled with a bilinear algorithm (when resolution is set I guess, maybe extent too)
• [ ] If it fails now it returns an empty DataArray, shouldn't it just raise an error?
• [x] Add attributes coordinates to the returned DataArray. Maybe look whether we could directly read the data with xarray.open_rasterio? Or with rioxarray
• [x] It'd be nice to directly obtain multiple bands in a xarray.DataSet. band could maybe become bands and accept either a string or a sequence of strings (bands). Or it could be another method.

[sbrunato]

• Make the parameters crs, resolution and extent optional
• Document the fact that the data is resampled with a bilinear algorithm (when resolution is set I guess, maybe extent too)

See #25 for optional parameters, also bilinear algorithm is not used by default any more