#18 mzML writer created files don't validate

[Steffen Neumann]

Hi, when writing mzML, the resulting files don't validate with the OpenMS validator.
Several of the problems are highlighted in https://github.com/sneumann/mzR/issues/151#issuecomment-374874216
Example code writing mzML from mzR (using the pwiz MSData as backend) is here:
https://github.com/sneumann/mzR/issues/151#issuecomment-375676951

Patches to fix these were created by Johannes Rainer (EURAC) and are available from
https://github.com/sneumann/mzR/pull/153
in particular for pwiz/data/msdata/IO.cpp and pwiz/data/msdata/Serializer_mzML.cpp

Yours, Steffen