Point to old Julia version and add missing files and readme

Edited mcmc.jl and directoryscanner.py so that the multinomial filter uses julia version 0.2.0-rc1. This allows the multinomial filter to run without errors.

Added some missing files such as V3.model to synchronize this repo with the /opt/NGSpipeline/ folder on Silverback. This allows tropism prediction to run without errors.

Added short readme.

After these changes directoryscanner.py runs mostly error-free, barring a couple of qfilt errors that are probably data-specific.