Recover old GPU code

These changes were in preparation for a poster for CNS 2013, that
subsequently were forgotten and lost, but are far more functional
than the code currently in repo trunk. Back from the future, baby!
reorganize debug device code
add notebook demo of gpu parsweep
Merge branch 'gpu-jul-2013' into merge-gpu

Conflicts:
	tvb/simulator/backend/tvb.cu
	tvb/simulator/coupling.py
	tvb/simulator/demos/debug_device.py
	tvb/simulator/models.py
	tvb/simulator/plot/tools.py
	tvb/simulator/simulator.py