Make regression-testing deterministic and add mspsim as a submodule instead of as a binary mspsim.jar file

This pull request several issues:
* Up to now the regression tests were initialized with a random seed. This made the regression test results random. It is now possible to set the seed using the command line and the regression test set this to 1 (which is as good as any other seed).
* MSPSim now obays the CCA-Threshold. As noted in https://github.com/mspsim/mspsim/pull/18 this breaks the regression tests. The CCA-Threshold is now set to -46 on Sky motes. This should also improve results from real testbeds.
* The previous changes will hopefully make Adam's submodule-patch go through Travis.

As the the random seed is not set in the simulation but passed as command line parameter this allows to extend the test system to run the same simulation with different seeds using different make targets.