merge AddressIndex into master

[cryptozeny]

addressindex is originally suggested by
https://github.com/bitpay/insight

BTC declined merge into master, but they want to keep another repo.
bitcoin/bitcoin#10370

but its enabled only with -addressindex like txindex=1 and its bool so RAM usage is not affected
https://github.com/sugarchain-project/sugarchain/blob/API-addressindex/src/validation.cpp#L218

ZEC and RES have also addressindex
https://github.com/ResistancePlatform/resistance-core/blob/master/src/addressindex.h

if we merge this AddressIndex into master, i wanna do after Yespower PoW cache is finished. this is safer IMO.
@volbil