Add fromTimestamp and toTimestamp to Blocks API endpoint

[Lemii]

Expected behavior

Filter block results by fromTimestamp and toTimestamp.

Actual behavior

Currently there is no way to retrieve data from a specific range of blocks using timestamps.

This would be a great feature for (forging) delegates who'd like to make detailed reports of their (daily, weekly, monthly or yearly) forged blocks.

Example: Get all forged blocks for delegate tembo from 2018/07/01 to 2018/08/01:
https://node01.lisk.io/api/blocks?limit=100&fromTimestamp=66286800&toTimestamp=68965200&offset=0&generatorPublicKey=326bff18531703385d4037e5585b001e732c4a68afb8f82efe2b46c27dcf05aa&sort=height%3Aasc

Which version(s) does this affect? (Environment, OS, etc...)

>1.0

[simonmorgenthaler]

Great suggestion!