only compute virtual band by the writeOp if should write
Merge pull request #25 from lveci/writeop_compute_virtband

only compute virtual band by the writeOp if should write
moved velocity metadata processing to metadata package
[BEAM-1688] Detection of reprocessing version fails
Use normalised longitude
additional meta parameter - intermediate
BEAM Python fixes:

[BEAM-1691] BEAM Python tests require specific test product
[BEAM-1690] BEAM Python examples often generate zero-valued output
Merge branch 'master' into nestmod