removeDefaultAttributeValue: Special-case order attribute
Created by: nthykier
Scour tried to handle "order" attribute as a SVGLength. However, the "order" attribute can consist of two integers according to the SVG 1.1 Specification and SVGLength is not designed to handle that.
With this change, we now pretend that "order" is a string, which side steps this issue.
Closes: #189 (closed) Signed-off-by: Niels Thykier niels@thykier.net