Improve GetMiningInfoResult.
Improve GetMiningInfoResult.

This commit modifies the types of the GetMiningInfoResult to better match
their underlying types.  While the information was all available and
accurate, it's nicer to treat numeric values as proper types instead of
all float64s.

Also, a new networkhashps field has been added for compatibility with the
reference implementation.

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