Remove define for RF_CHANNEL. It is already set in contiki-conf.h
Allow setting the CCA-threshold for Sky motes. Dafault: -46
This adjustment is needed due to commit 0a13f99 in mspsim. As promised
in https://github.com/mspsim/mspsim/pull/18 it broke the regression
tests.
Added mspsim as a submodule instead of as a binary mspsim.jar file
Make simulation output more verbose when using a CI