Create crypto provider that uses the crypto client defined in #15 to implement crypto ops

[davram-code]

Implement a Java Cryptographic provider as specified in [1] that will use the #15 client to implement the following functionalities:

• ECDSA
• Key pair generatuon
• ECIES encryption

[1] - https://docs.oracle.com/javase/9/security/java-cryptography-architecture-jca-reference-guide.htm#JSSEC-GUID-A7EEDE25-C4C0-4C28-94EA-262858AE9212 [2] - http://ld2016.scusa.lsu.edu/java/7-docs/technotes/guides/security/crypto/HowToImplAProvider.html