* dtls/openssl.py:
- Added utility fucntions EC_curve_nist2nid() and EC_curve_nid2nist()
* dtls/patch.py:
- Extended wrap_socket() arguments with callbacks for user config functions of ssl context and ssl session values
- Extended SSLSocket() arguments with callbacks for user config functions of ssl context and ssl session values
* dtls/sslconnection.py:
- Extended SSLConnection() arguments with callbacks for user config functions of ssl context and ssl session values
- During the init of client and server the corresponding user config functions are called (if given)
- Added new classes SSLContext() [set_ciphers(), set_sigalgs(), set_curves(), set_ecdh_curve(), build_cert_chain(),
set_ssl_logging()] and SSL() [set_mtu(), set_link_mtu()]