Read password protected keys in Java

[GoogleCodeExporter]

I've implemented password-protected keys for Java Keyczar, that are compatible 
with the format generated by the C++ implementation: 
https://code.google.com/p/keyczar/wiki/CppTutorial#Using_PBE_(password-based_enc
ryption)_to_encrypt_keys

The code is in the following clone:

https://code.google.com/r/ej-pbe-java/

Happy to make changes as desired! I'd love to see this merged upstream. One 
possible improvement is to fix GenericKeyczar to accept the "encrypted: true" 
JSON data, to avoid the hack in getMetadata().

Original issue reported on code.google.com by e...@evanjones.ca on 25 Nov 2013 at 3:41