* Code Janitor time! Many fixes and documenting fixes that should be
done in the future. for the most part, this is a general code cleanup.
* On smaller/embedded systems, the "final" keyword cleanups will have
more of an impact than on larger systems.
* Document missing hashCode() methods.
* Unhide more variables to make code easier to read.
- Add a signed Certificate type
- Add a main() to PrivateKeyFile to generate
Destinations with various Certificate types
- Add a VerifiedDestination class to check Certificates
of various types
- Add a HashCash library from http://www.nettgryppa.com/code/
(no distribution restrictions)
- Allow non-null Certificates in addressbook
