[LoadDigraph] Colour attribute does not take multivalue

[harshsikhwal]

Files: Resources\test[LoadDigraph] Colour attribute does not take multivalue\multi_color.dot

Attributes with multiple values do not take all the present values:

graph { ethernet [ color = "green, brown, red, black", label = "ethernet", shape = "circle" ] }

is generated as:

graph Default { ethernet [ color = "green", label = "ethernet", shape = "circle" ] }

This is applicable to attributes having support for multivalues.