This function returns the name of the column in e_meta that contains the mapping variable IDs.
get_emeta_cname(omicsObject)an object of the class 'pepData', 'proData', 'metabData',
'lipidData', 'nmrData', 'statRes', or 'trelliData', usually created by
as.pepData, as.proData,
as.metabData, as.lipidData,
as.nmrData, imd_anova, or
as.trelliData respectively.
a character string describing e_meta cname