Standardize function names

[wleoncio]

The names of DIscBIO functions are not consistent: some use Pascal case (e.g. ClassVectoringDT, PCAplotSymbols), others use Dromedary case (e.g. clustheatmap, plotGap); even the spelling of similar functions can change (e.g. plotOrderTsne vs. plotLabelstSNE). This can cause confusion on a user. It would be great if all functions had a naming convention.

[wleoncio]

This is a major change which is better left to a future (not next) release.