What are the rules for cricket's new format 'The Hundred'?

The Hundred will begin in UK today. It will feature 100 balls per innings. Bowlers can deliver either five or 10 consecutive balls and a maximum of 20 balls per match. The first 25 balls in each innings will be Powerplay, where only two fielders are allowed to be stationed outside the inner ring. No-balls will be worth two runs.