accept server cert permanently

when you svn up through ra_dav on an https server with self-signed
certificate, you get prompts about unknown certificate issuer etc.

there should be an option to remember permanently the certificate
authority

<sander> Ah, you can put the ca.cert at a public location and tell
them to download that
<TTimo> so there's no way to retrieve the cert as part of the https
negociation?
<TTimo> no workie ?
<sander> Yes, do workie :)
<sander> neon could do it aswell.  We just need to add code to do it
<sander> You can file a post-1.0 issue for it

Original issue reported by timot