Base64 encoder/decoder

Hi there,

just wrote a simple base64 encoder/decoder which seems to work. I'm submitting this that early so you can have a look at it and tell me, for example, if it could be made simpler or beautifullier with some ooc niceties I forgot.
Especially: Should I use real arrays instead of `Octet*`? And should this even be part of the SDK?
Also, I need to write tests for that. What's the best place to but test code at the moment?

Cheers!