A phased.maplist, with linkage group names LG1 etc. Each list item is a data.frame with columns marker, position followed
by the phased map, coded in 1 and 0 for presence/absence of SNP (alternative) allele on parental homologues (h) numbered 1:ploidy for parent 1
and ploidy + 1 : 2*ploidy for parent 2.