Added list of asymptomatic patients

List of asymptomatic patients taken from Victor's presentation, and
appointed by Shenia.
Added database files for multiple visits
Plot silhouette.
Split plotting routines into functions.
Edit in scrap file.
XLS file reads with a column of NaN's.

Check later what's wrong with it, or create a new one with this
patient's data.
Mark end of function
Track patient visits