Clean up and fix account and nonce registry error

[haerdib]

• summarizes accout and nonce registry erros to one enum
• fixes rpc error return values to not be always "nonce uninitialized"
• fixes outdated python script cancel-order request
• client now prints success message if cancel_order does not return an error

Output now looks like the following:

./substratee-client -p 9994 -P 2094 trusted cancel_order --accountid=//Alice --orderid=oijef03jaf --marketbase=btc --marketquote=usd --mrenclave=9DEggF3cbcuumAjsanchCnsbVjTURqkmUP1PekSWuv7x --direct
[Error] RPC call failed: Authorization error: AccountNotRegistered

./substratee-client -p 9994 -P 2094 register-account //Alice
[+] Transaction got finalized.. Hash: 0x3b5350dc1af8d821e28c4a8d30055985932d3b7daceab273e1631f2878d4856e

 ./substratee-client -p 9994 -P 2094 trusted cancel_order --accountid=//Alice --orderid=oijef03jaf --marketbase=btc --marketquote=usd --mrenclave=9DEggF3cbcuumAjsanchCnsbVjTURqkmUP1PekSWuv7x --direct
[Error] RPC call failed: OpenfinexWebSocketError("\"Failed to send request\"")

(interpretation: cancel_order gets through until openfinex client, hence fixing issue #270)

[zktony]

LGTM