Add java Base64 from Apache commons

[johnynek]

I removed two interfaces and moved code from their stringutils class.

We got bitten by version issues on commons, I think having bijection-core having no dependencies is a worthy goal.

[mosesn]

Wait, won't this break compatibility for everyone who uses the apache BigInteger? They can stop using apache.BigInteger and start using bijection.BigInteger manually, but if they have libraries which depend on it, they're out of luck. I think it would be better to just move this all into a subproject.

[johnynek]

This only removes a dependency, they can still use apache Base64 (if that is what you mean), just add an explicit dep in their project (and we use a different package name so everything should be good).

The BigInteger stuff was just a bijection from BigInt to java BigInteger (I'm a little confused here about your comment).

[mosesn]

You're right, I was confused. I thought that there was a bijection from X to some apache class that you changed to being a bijection from X to a copied file. My mistake!