Break BitPay into a sub-module.

Since BitPay, Coinbase, and Blockchain all have APIs, I figured I'd scope creep and bundle them all into one project. That meant just doing a hook_commerce_currency_info() in a base module, then letting a separate BitPay module handle that processor. I also took advantage of the Libraries API instead of taking on the maintenance burden of remote API libs since Coinbase has a sizable library. There's also a license issue that's unknown since both BitPay and Coinbase neglected to include a license with their API libraries.