merge #857: add `difficulty` in `getchaintips` output for convenience
merge #857: add `difficulty` in `getchaintips` output for convenience

a50861e add `difficulty` in `getchaintips` output for convenience
terracoin/terracoin,aspirecoin/aspire,schinzelh/dash,diggcoin/diggcoin,thelazier/dash,rsdevgun16e/energi,BlockchainTechLLC/3dcoin,willwray/dash,rdqw/sscoin,Petr-Economissa/gvidon,crowning-/dash,PandaPayProject/PandaPay,crowning-/dash,lakepay/lake,lakepay/lake,ediston/energi,biblepay/biblepay,terracoin/terracoin,dmrtsvetkov/flowercoin,dashpay/dash,biblepay/biblepay,aspirecoin/aspire,UdjinM6/dash,biblepay/biblepay,willwray/dash,projectinterzone/ITZ,rsdevgun16e/energi,schinzelh/dash,dashpay/dash,Petr-Economissa/gvidon,BlockchainTechLLC/3dcoin,jmgilbert2/energi,projectinterzone/ITZ,Petr-Economissa/gvidon,ionomy/ion,biblepay/biblepay,terracoin/terracoin,diggcoin/diggcoin,dashpay/dash,rdqw/sscoin,crowning-/dash,worldbit/worldbit,nmarley/dash,dashpay/dash,dmrtsvetkov/flowercoin,willwray/dash,Petr-Economissa/gvidon,terracoin/terracoin,ivansib/sib16,lakepay/lake,jmgilbert2/energi,projectinterzone/ITZ,schinzelh/dash,jmgilbert2/energi,HeliumGas/helium,PandaPayProject/PandaPay,diggcoin/diggcoin,HeliumGas/helium,terracoin/terracoin,aspirecoin/aspire,lakepay/lake,nmarley/dash,worldbit/worldbit,PandaPayProject/PandaPay,jmgilbert2/energi,HeliumGas/helium,ionomy/ion,BlockchainTechLLC/3dcoin,aspirecoin/aspire,diggcoin/diggcoin,HeliumGas/helium,lakepay/lake,nmarley/dash,worldbit/worldbit,ivansib/sibcoin,RyanLucchese/energi,thelazier/dash,alejandromgk/Lunar,willwray/dash,ivansib/sibcoin,willwray/dash,ivansib/sibcoin,RyanLucchese/energi,biblepay/biblepay,terracoin/terracoin,rdqw/sscoin,nmarley/dash,dashpay/dash,alejandromgk/Lunar,aspirecoin/aspire,ionomy/ion,nmarley/dash,thelazier/dash,alejandromgk/Lunar,thelazier/dash,lakepay/lake,jmgilbert2/energi,BlockchainTechLLC/3dcoin,Petr-Economissa/gvidon,diggcoin/diggcoin,PandaPayProject/PandaPay,ionomy/ion,rsdevgun16e/energi,schinzelh/dash,dmrtsvetkov/flowercoin,RyanLucchese/energi,crowning-/dash,worldbit/worldbit,PandaPayProject/PandaPay,ediston/energi,dmrtsvetkov/flowercoin,dmrtsvetkov/flowercoin,aspirecoin/aspire,ediston/energi,ionomy/ion,HeliumGas/helium,crowning-/dash,rsdevgun16e/energi,HeliumGas/helium,BlockchainTechLLC/3dcoin,thelazier/dash,RyanLucchese/energi,biblepay/biblepay,willwray/dash,rdqw/sscoin,nmarley/dash,ivansib/sibcoin,RyanLucchese/energi,projectinterzone/ITZ,diggcoin/diggcoin,worldbit/worldbit,PandaPayProject/PandaPay,rdqw/sscoin,Petr-Economissa/gvidon,biblepay/biblepay,BlockchainTechLLC/3dcoin,ivansib/sib16,biblepay/biblepay,ediston/energi,rsdevgun16e/energi,schinzelh/dash,ivansib/sib16,UdjinM6/dash,schinzelh/dash,alejandromgk/Lunar,nmarley/dash,ediston/energi,ivansib/sib16,UdjinM6/dash,ivansib/sibcoin,rsdevgun16e/energi,alejandromgk/Lunar,UdjinM6/dash,rdqw/sscoin,RyanLucchese/energi,ivansib/sib16,ionomy/ion,projectinterzone/ITZ,ediston/energi,ivansib/sibcoin,crowning-/dash,alejandromgk/Lunar,ivansib/sib16,dmrtsvetkov/flowercoin,worldbit/worldbit,UdjinM6/dash,jmgilbert2/energi