Move json errors to btcjson and call from there.
Move json errors to btcjson and call from there.

ok jrick@

jrick/btcwallet,Stash-Crypto/btcwallet,Stash-Crypto/btcwallet,jrick/dcrwallet,Roasbeef/btcwallet,jrick/dcrwallet,synrg-labs/btcwallet,jrick/btcwallet,btcsuite/btcwallet,decred/dcrwallet,Roasbeef/btcwallet,decred/dcrwallet,synrg-labs/btcwallet,btcsuite/btcwallet