More hashing functions - SHA-1, SHA-224, SHA-256 and HMAC

I've been distracted by implementing hashing algorithms. I've extended the COM.CURLR.CRYPTO package with classes for SHA-224 and SHA-256 (plus my own SHA-1 for consistency) hashing algorithms. And I've included classes for creating HMACs (keyed-hash message authentication codes) for all these and for MD5.

The Security Hash Standards (SHS) are comprehensively documented in FIPS PUB 180-2, which you can find at NIST, along with much else concerning cryptographic standards. There's a validation standard too, and though I don't think I'll get the code certified, the implementations do pass the sample tests for byte implementations. I've included those tests in the curlr repository - with the caveat that the data files are from NIST, not me.