There are two 5 star svg upload plugins: safe svg and svg support. I have tested both and found svg support better because it has svg upload restriction in free version but if you want to restrict svg upload with safe svg plugin, should pay for premium version.
Hi Richard, this post is quite old, Retina option came just after this post. The SVG route is the way to go for vectors, and the GP 2.2 Beta now includes a Logo width so no need for CSS sizing of an SVG