updating ecc.py wich ecdsa

[gstarovo]

• i have made changes in the keyexchange.py that are regarding encoding and decoding functions from ecc.py
• i have deleted the corresponding functions from ecc.py and test
• i tried to implement changes into getCurveByName, but faced several issues:
  • not supported names as we discussed ('secp256r1', 'cesp192r1')
  • supported names, that according to test should not be accepted ('NIST256p' as a name)
• i did not implement changes in the getPointByteSize function, as it returns the size of the r of the signature and implementing it with only ecdsa seems to be more complicated solution, than the one that already exists. maybe i am wrong.
• added minor change in the keyexchange.py: generating random private key with ecdsa library

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This change is 

[tomato42]

instead of deleting the branch you can force push the changes to the same branch