Rudder

We need to document how to update the Policy Template / Technique library for a running version of Rudder.

This should be fully documented, for those using 2.3 / 2.4 (although some changes will most likely be made for 2.4), to use the packages provided on rudder-project.org. It is imperative to explain where packages install files, what commands to run to update the library, and don't forget that in 2.4 system Techniques are upgraded automatically.

This should be done in the 2.3 docs, and then ported to 2.4 documentation guide