Add support for transferring native EC keys into and out of JWK representation

[Justin Richer]

java.security.interfaces has several native classes to represent EC keys that the JWK representation (ECKey) should be able to translate between:

ECKey ECPrivateKey ECPublicKey

There is already support for this type of function in both RSAKey and OctetSequenceKey.

[Vladimir Dzhuvinov]

Useful howto from BouncyCastle:

http://www.bouncycastle.org/wiki/display/JA1/Elliptic+Curve+Key+Pair+Generation+and+Key+Factories

[Vladimir Dzhuvinov]

Done in commit 6a06375 :)