EdDSA: Use BouncyCastle implementation.

[sundbry]

Hi Buddys,

Since BouncyCastle published their EdDSA implementation, loading key files using buddy.core.keys/public-key and buddy.core.keys/private-key started loading the BC key classes instead of those from net.i2p.crypto. Since I was not using jwks in my app this was a problem.

I went ahead and replaced the original library with the BouncyCastle implementation, and removed the dependency.
There is one minor issue with this implementation which may cause JVM security or reflection warnings The constructor to this class is not public, so we use some reflection hacks to access it. https://github.com/bcgit/bc-java/blob/bc3b92f1f0e78b82e2584c5fb4b226a13e7f8b3b/prov/src/main/java/org/bouncycastle/jcajce/provider/asymmetric/edec/BCEdDSAPrivateKey.java#L32

I will be submitting a PR to BouncyCastle to open that constructor up in the meantime.

Stack trace for reference on the original issue

ERROR in (test-algorithms) (EdDSAEngine.java:134)
Uncaught exception, not in assertion.
expected: nil
  actual: java.security.InvalidKeyException: cannot identify EdDSA private key: class org.bouncycastle.jcajce.provider.asymmetric.edec.BCEdDSAPrivateKey
 at net.i2p.crypto.eddsa.EdDSAEngine.engineInitSign (EdDSAEngine.java:134)
    java.security.SignatureSpi.engineInitSign (SignatureSpi.java:131)
    java.security.Signature.initSign (Signature.java:657)
    buddy.core.dsa$eval15659$fn__15660.invoke (dsa.clj:79)
    buddy.core.dsa$eval15563$fn__15594$G__15550__15601.invoke (dsa.clj:47)
    buddy.core.dsa$sign.invokeStatic (dsa.clj:159)
    buddy.core.dsa$sign.invoke (dsa.clj:156)
    buddy.sign.jws$fn__15957.invokeStatic (jws.clj:66)
    buddy.sign.jws/fn (jws.clj:31)
    buddy.sign.jws$calculate_signature.invokeStatic (jws.clj:109)
    buddy.sign.jws$calculate_signature.invoke (jws.clj:103)
    buddy.sign.jws$sign.invokeStatic (jws.clj:144)
    buddy.sign.jws$sign.doInvoke (jws.clj:136)
    clojure.lang.RestFn.invoke (RestFn.java:442)
    buddy.sign.jwt$sign.invokeStatic (jwt.clj:123)
    buddy.sign.jwt$sign.invoke (jwt.clj:117

[niwinz]

I will review it tomorrow probably. Thanks!

[niwinz]

Having that BC rejected the issue, i'm a little bit worried with the reflection. I'm going to merge this, but if some isse appears, i will probably revert this.

Thanks.