Investigate splitting authentication and keyx factories by local versus remote

[wmiaw]

To make things easier on the MSL configurator, it makes sense to have a conceptual difference between local and remote authentication and keyx factories. So one can specify different schemes and behaviors depending on if the operation is occurring for the local or the remote entity.

This may not work well with the current code design, which does not really differentiate between local and remote except at the highest / outer-most code layers. So this needs to be investigated.