accept results from qmethod::qmethod as pcobj

[Max Held]

qmethod is a CRAN package that does Q methodology, which is basically a factor analysis with the data table turned sideways, so that there are people-variables and item-cases (weird, I know).

qmethod essentially wraps psych::principal (plus some bells and whistles), so it should be possible to extract a pcobj from it so it can be used as an input to ggbiplot() (which is great).

This duplicates much, though not all, of #17