First steps for adding a simulator to OSS7.
The goal is to be able to run integration tests and debug the stack on PC instead of on the target hardware.
Building the stack using the "SIM" driver for both phy and hal driver allows to run the stack inside the simulator.
The simulator is based on Castalia 3.2 (which is in turn using OMNeT++).
A manual will follow later.
Merge branch 'sim'