implement the col parameter for subgraphs of plot graphs

[thioulouse]

data(meau)
env <- meau$env
sites <- meau$design$site
envpca <- dudi.pca(env, scannf = FALSE)
betsite <- bca(envpca, sites, scannf = FALSE)
plot(betsite, row.col=1:6)
plot(betsite, row.pellipse.col=1:6)

[sdray]

It works now (corrected by this commit) but we need to correct this last bug:

plot(betsite, col=1:6)
#or 
plot(betsite, col=TRUE)

[aursiber]

As the col argument is distributed to all subgraphs, the subgraphs row (s.class top-right) and eig (plotEig bottom-left) should be updated with the new colors (see below). Is this what we want?

On the other hand, there is confusion between the col argument and the col subgraph. This is also the case for many other ade4 functions (plot.discrimin, plot.within, plot.dpcoa, plot.mcoa, plot.foucart, plot.mfa, plot.pta, scatter.dudi, scatter.coa, scatter.nipals, kplot.mfa, kplot.sepan, kplotsepan.coa, kplot.statis) which plot one or more subgraphs defined by an argument whose name begins by col (col, colB, collections).

[sdray]

In this example, it should apply only on the s.class plot and s.label (Classes). The argument should be probably treated separately before the call to sortparamADEgS and associated to the corresponding plot. For other functions, the behavior will be different