Changes

Findbugs and lint (thx zzz)

Add missing synchronized
Closes #10

Final the APIs

Implement key encoding and decoding
Follows the docs for java.security.spec.PKCS8EncodedKeySpec and the
draft at https://tools.ietf.org/html/draft-josefsson-pkix-eddsa-04
Ignores the example in the josefsson draft, required for keytool to
work.
Closes #13 I2P ticket: https://trac.i2p2.de/ticket/1723
Signed-off-by: str4d <str4d@mail.i2p>

Implement hashCode() and equals() fully
- Add hashCode() and equals() everywhere it was missing, so we can test
keys for
 equality: Curve, EdDSAParameterSpec, EdDSAPrivateKey, and
EdDSAPublicKey
- Speedup for GroupElement.equals()
Signed-off-by: str4d <str4d@mail.i2p>

Implement one-shot methods in EdDSAEngine
The one-shot methods can be used to improve performance by not copying
the data if all the data is available. They are unsupported by the Java
JCA and must be used directly.
This commit also fixes an API violation if EdDSAEngine object is reused
for signing.
I2P ticket: https://trac.i2p2.de/ticket/1750
Signed-off-by: str4d <str4d@mail.i2p>

Precedence fix