Python snappy sen2cor plugin

Using snappy and the tool adapter should work but it is just an indirection.

I think the best way to use sen2cor from Python is explained in the
[Sen2Cor Configuration and User Manual - V2.10.0 (esa.int)] (http://step.esa.int/thirdparties/sen2cor/2.10.0/docs/S2-PDGS-MPC-L2A-SUM-V2.10.0.pdf) section 3.4 The Software Development Environment.

To use it directly as API was als requested several times. But I think this is still not possible.

It seems sen2cor is still using Python 2.7. This can cause conflicts if you use Python 3.