Own certs for Plugins

[echelon]

Hi

Small lines for adding certs to your I2P router to accept own certs:

* mkdir -p ~/.i2p/certificates/plugin
* copy the certificate file in there
* should work without a restart
* looks like the CN has to match the signer name
* must be signer.crt, where "signer" is the signer name like you_at_mail.i2p
* have to replace @ with _at_

After creating a plugin, there should be ~/.i2p-plugin-keys/plugin-su3-public-signing.crt

For .sud you can set advanced config setting:
routerconsole.allowUntrustedPlugins=true