BUG: glass brains still don't save as svg, svg files can have transparent elements

[wiheto]

Problem with set_rasterized and alpha interacting. Works when template_style='surface' but not with glass.

[wiheto]

Another bug noticed with svg files is that if there are two edge colors using the new edge_color as dict input, one of the inputs can be rendered transparent as svg. Likely a zorder problem