Add nativeID output in mzIdentML/pepXML[/mzML/PIN]

[chambm]

To preserve Waters and Sciex source spectrum links, writing nativeID in the output pepXML/mzIdentML is necessary. Please read in the nativeID when reading spectra and pass it through when writing pepXML/mzIdentML elements for those spectra. It would be good to preserve it in mzML as well, but that's not as important. If the format allows, it might be helpful to write it in Percolator PIN format as well so it's simple to map PIN lines to the mzIdentML/pepXML equivalent.

Thanks!