logical timestamp indexing of block hashes

[braydonf]

Tested with livenet and testnet, with these branches for insight-api, bitcore-node and bitcoind-rpc:

• https://github.com/bitpay/bitcore-node/pull/473
• https://github.com/bitpay/insight-api/pull/490
• https://github.com/bitpay/bitcoind-rpc/pull/18

Looks like around 4 percent of block timestamps were adjusted with logical timestamp for livenet. Confirmed that the blocks overview page in Insight no longer skips blocks (https://github.com/bitpay/insight-ui/issues/714) and is in block order by default.

[braydonf]

Did another reindex and times have remained the same at around 12-14 hours for livenet.

[braydonf]

ACK 36f5ee5ff37c4b27f9d50db5ef975f792bf7c71a