The title says it all actually. Added special custom data type, because we don't know in advance whether we're referencing UV or Color layer. Also made it so vertex attributes are normalized. TODO: Border render in viewport ignores the normalization of the attribute array for some reason, will be looked into still. Reviewers: mont29, brecht, campbellbarton Reviewed By: brecht, campbellbarton Differential Revision: https://developer.blender.org/D2022