Simplify S1 Tiling installation w/ OTB binaries

OTB binaries don't ship GDAL Python bindings, nor gdal-config, while they ship libgdal.so and it's include files.

As such installing GDAL Python bindings is not as transparent as we could expect for S1 Tiling end-users.

Note, this relates to OTB issues:

• orfeotoolbox/otb#2041 (closed)
• and orfeotoolbox/otb#1523 (closed)