[LoadDigraph] Colour attribute does not take multivalue

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.