Full version is used as the su3 version.
Uses same su3 certs as release updates. Users may add additional certs
to ~/.i2p/certificates/router/ as necessary.
Copy echelon's reseed key for use as a router signer.
Unsigned update remains a separate option for now.
Various update subsystem cleanups.

  - Generate su3 file in release target
  - Add my new RSA 4096 pubkey cert for updates
  - Fix checkcerts.sh