feature(node): adding global for chain tips
feature(node): adding global for chain tips

Adding a global for the best block for a given chain or network. Reduces need to call "getChainTip"

martindale/bitcore,bitjson/bitcore,martindale/bitcore,martindale/bitcore,bitpay/bitcore,martindale/bitcore,bitpay/bitcore,bitpay/bitcore,bitpay/bitcore,bitjson/bitcore,bitjson/bitcore,bitjson/bitcore