Incorporate referenceableParamGroupRef accessions

Added a way to determine if referenceableParamGroupRef was being used
and to incorporate the accessions there when populating accession data.
Revert "Incorporate referenceableParamGroupRef accessions"

This reverts commit cdbf8bd7b2993bd5d0cbb7a7abeb9eeda1397e65.
gitattributes
Accession asignment from ParamGroupRef

Some mzML files use referenceableParamGroupRefList elements to asign
repeated accession elements.
Revert "gitattributes"

This reverts commit ca2d913a3abff7c1d07a83b451345114860aef9b.
Merge pull request #21 from SiggiSmara/featureAdd

Adding a way to deal with referenceableParamGroupList elements