Change to HigherDimensionProcessingParameterSetType
Fixes #8 Rename Spectrum2D element.
Fixes #9 rename AcquisitionDimensionParameterSet.

Rename AcquisitionDimensionParameterSet to
AcquisitionDimensionParameterSetType
Merge branch 'hackathon' of github:nmrML/nmrML
Merge branch 'master' of https://github.com/nmrML/nmrML into hackathon