Fix symbol render

Fixed a bug that was not transferring the transform attribute from use tag to cloned tag.
Added attribute "instanced_by_use" to tags cloned to divide symbols from used symbols.
Added symbol to the list of tags not to be rendered ( if not instanced )
Changeg viewbox transform function to take care of all the tags that can support viewbox attribute.
For tags that are not svg, scale factor is ignored till we can sort out how to use 100% value for width attribute
Not sure this is a good wording. Do you mean "referenced in use tag"?