Modesense6

Add initial MODESENSE6 and the page we need for media changers ElementAddressAssignments
We will need to add a large number of additional pages over time, but this is enough for talking to a medium changer.

Add initial support for READELEMENTSTATUS. This makes it possible to query a medium changer about what media is loaded and where.

Add a new tools directory. This directory can be used to store example code that is NOT part of the build/install. Add a simple mtx.py tool here. This tool aims to be a mtx replacement but we only support the 'status' command so far. This tool can be useful when developing and testing SMC commands as they are added.

So far, this is the only thing that mtx.py supports :

mtx.py -f /dev/changer status