calcPotShifts: Calculate potential shifts in marker dosages
In mdavy86/polymapR: Linkage Analysis in Outcrossing Polyploids

Internal function for correctDosages function

1	calcPotShifts(segtypes, ploidy)

`segtypes`	Vector of segregation types
`ploidy`	The ploidy of the species

Data.frame with columns:

`segtype`	The segtype code before the underscore i.e. without the first dosage class
`mindos`	The first dosage class
`shift`	-1, 0 or 1: potental shifts to try out for each segtype whether a shift of +/- 1 should be tried or not (0) (only when number of dosages in segtype in <= ploidy-2 and min.dosage==1 or max.dosage==ploidy-1)