Improve rpcserver.
Improve rpcserver.

Add getdifficulty command to rpcserver.

Add missing error check in an old bit of rpcserver.

Add getbestblockhash command.

toddfries/btcd,sysbot/btcd,jcmincke/dcrd,jrick/dcrd,aakselrod/btcd,pkothbauer/btcd,qchain/btcd,mathiasrw/btcd,danoctavian/btcd,btcsuite/btcd,dan-da/btcd,tb00/btcd,BitGo/prova,wallclockbuilder/btcd,mathiasrw/btcd,toddfries/btcd,cjepson/btcd,DanielKrawisz/btcd,jcmincke/dcrd,btcsuitereleases/btcd,wallclockbuilder/btcd,dan-da/btcd,jcmincke/dcrd,qchain/btcd,FactomProject/btcd,davecgh/btcd,adiabat/btcd,hectorj/btcd,jongillham/btcd,Cleawing/btcd,Evil-Coin/Evil,jongillham/btcd,ltcsuite/ltcd,Dirbaio/btcd,dajohi/btcd,jrick/dcrd,Dirbaio/btcd,runeaune/btcd,Dirbaio/btcd,ppcsuite/ppcd-old,aakselrod/btcd,Roasbeef/btcd,jimmysong/btcd,danoctavian/btcd,Evil-Coin/Evil,glv2/ppcd,adiabat/btcd,btcsuitereleases/btcd,soapboxsys/ombfullnode,BitGo/prova,CryptocurrencyCabal/htcd,cqswxj2013/btcd,Cleawing/btcd,dajohi/btcd,FactomProject/btcd,runeaune/btcd,stevenroose/btcd,Stash-Crypto/btcd,cqswxj2013/btcd,ppcsuite/ppcd,btcsuite/btcd,1d4Nf6/btcd,dajohi/btcd,decred/dcrd,DanielKrawisz/btcd,hectorj/btcd,ltcsuite/ltcd,1d4Nf6/btcd,decred/dcrd,Stash-Crypto/btcd,jrick/btcd,stevenroose/btcd,CryptocurrencyCabal/htcd,cjepson/btcd,sysbot/btcd,glv2/ppcd,soapboxsys/ombfullnode,jrick/btcd,pkothbauer/btcd,ppcsuite/ppcd,ppcsuite/ppcd-old,Roasbeef/btcd,jrick/btcd,jimmysong/btcd,davecgh/btcd,tb00/btcd