Add more dim-reduction methods for `plot(ce)`

[pat-alt]

Currenlty, only MultivariateStats.PCA is working properly. Basic code for ManifoldLearning.TSNE and hence also other methods shipped with that package is also there, but predict(tfn<:TSNE) does not accept a second positional argument, i.e. new data (whereas PCA does).

Perhaps of interest @RaunoArike @kmariuszk @VincentPikand