SCExV using the R S4 object as backend

Completely move from the R S3 object that is part of the SCExV server to the Rscexv S4 package.
Benefits:

1. The R object has advanced plotting functions using the Heatmap.3 functionality and some ggplot function.
2. All groupings stay accessible in the web frontend
3. If two normalization functions are run in the same session all old data stays available in the downloaded zip file.