All sidechain related wallet RPC commands should be prefixed with sc_

[cronicc]

We have a clear distinction between transparent address RPC commands (no prefix) and shielded address RPC commands (z_ prefix).

For some of the sidechain related RPC commands, the sc_ prefix was chosen, but not for all of them.

Wallet commands with sc_ prefix:

sc_create withdrawalEpochLength [{"address":... ,"amount":...,"wCertVk":...,"customData":...,"constant":...,...},...]
sc_send "address" amount "scid"                                                                                      
sc_sendmany [{"address":... ,"amount":...,"scid":,...},...]                                                          

Wallet commands without sc_ prefix:

create_sidechain {"withdrawalEpochLength":... , "fromaddress":..., "toaddress":... ,"amount":... ,"minconf":..., "fee":..., "wCertVk":..., "customData":..., "constant":...}
request_transfer_from_sidechain {TODO}           
send_certificate scid epochNumber quality endEpochCumScTxCommTreeRoot scProof [{"pubkeyhash":... ,"amount":...},...] (subtractfeefromamount) (fee)
send_to_sidechain {...}                                                                                                                           

The sc_ prefix should be added to all sidechain related wallet RPC commands to easily distinguish them. This should be done before the first official release of zend_oo, after the first release changing the API would be problematic.

Prefixing non-wallet related sidechain RPC commands with sc_ could also make sense, but I don't see it as important as for wallet section commands (discuss?).