Refactor neuronTypeToString() from Global.cpp

[stiber]

1. Rename to vertexTypeToString()
2. Move it to AllVertices
3. Should this be a utility function or a method?

Graphitti/Simulator/Utils/Global.cpp

Lines 56 to 70 in 62ad162

	// MODEL INDEPENDENT FUNCTION NMV-BEGIN {
	string neuronTypeToString(vertexType t)
	{
	switch (t) {
	case INH:
	return "INH";
	case EXC:
	return "EXC";
	default:
	cerr << "ERROR->neuronTypeToString() failed, unknown type: " << t << endl;
	assert(false);
	return nullptr; // Must return a value -- this will probably cascade to another failure
	}
	}
	// } NMV-END