Setup initial testsuite.
Abstract the Elliptic Curve used.

* Introduce crypto_util.BTC_CURVE as the curve's name. Replace any
  magic strings in the codebase with crypto_util.BTC_CURVE.
* Introduce the OpenSSL name and key length.
Abstract pubkey processing.

* Deprecate hexToPubkey.
* Streamline cryptor creation.
Abstract privkey creation.
Drop hexToPubkey.

* Replace with pubkey_to_pyelliptic.