Absolutely recommend the Olympus fl-600r, it ticks all of the boxes, and is very easy to use whilst still packing a lot of powerful features. That or the Panasonic FL-360L, which is the same flash with a different name.
Also do keep in mind while shopping around that while the Olympus FL-LM3 flash would appear to suit your needs, it won't work on older Olympus cameras like the 1st generation E-M5 - it requires an extra pin in the hot shoe to provide power to the unit, where older Olympus bodies had a micro-USB port beneath the hot shoe to provide power to accessories or flashes that don't use batteries.