advanced python plotting + perl scripts for transforming files.

- Added some advanced python plotting (with lots of command line options to turn on the features).
- "histo" is updated, and is backwards compatible (now the histograms look a bit better, and you can label the axes and specify the limits and compute a Gaussian kde).
- Added some perl scripts to select columns from files, take the mean, and do exponential or logarithmic transforms easily.
- Added a perl script to collate pdf files.