Allow to use the internal streaming strategy

[Rémi Cresson]

It could be nice to allow user to disable the explicit tiling strategy (hence not using the output image extended filename).
Typically, to use other file format that GeoTiff, e.g. jp2. The internal stream is handled internally in C++ with a custom filter that process the whole output in a streamable fashion, so it won't be a problem to process non-streamable output formats like jp2. We might add some --noexplicitstreaming or something, that disable the extended filename hardcoded in sr.py.