more mods to the front end including a visualiser vertex to remove all this dependancy between vis and vertex
fixed broken imports from changes in pacman structure and spinnman structure
attempt to fix
fxiing
Merge remote-tracking branch 'origin/master'

Conflicts:
	spynnaker/pyNN/models/abstract_models/external_device.py
	spynnaker/pyNN/models/abstract_models/population_vertex.py
	spynnaker/pyNN/utilities/memory_constants.py