Add more data pre-processing methodologies

[frehbach]

Are there any other packages which can be included, other than imputeTS?

• Core functions like:
  ** Scale
  ** Normalize (BBMisc?)

[SteffenMoritz]

center -> R base "scale"
scale / normalization - > R base "scale"
log - > R base
square root - > R base
differencing - > R base
box cox - > forecast "BoxCox"
YeoJohnson -> ?
PCA - -> entweder stats "princomp" (spectral decomposition) oder stats "prcomp" / ()FactoMineR "PCA" (singular value decomposition)

ica - independend components -> ?
“zv“: remove attributes with a zero variance (all the same value). ?
“nzv“: remove attributes with a near zero variance (close to the same value) ?