NanoLongRange Evo

This is my improvements (so far) to the great NanoLongRange concept by Dave_C_FPV.
This thing is about 80% of my flying time this season.

The most notable changes are:
* **Integrated battery tray** to make frame tougher and stiffer (and save a few grams).
* **Balanced pitch** to give more power to the motors and reduce propwash. The original NanoLongRange is 65:35 nose heavy which means front motors work almost twice as hard as rear ones during the flight. This is usually not such big of an issue for a more powerful quads, but this quad is very limited on power so balancing it improves the flight experience noticeably. This frame is perfectly 50:50 balanced and front props and propguards are still ~5mm out of sight of 4:3 ant camera.
* **Stronger arms** with angled top surface have a stiffer and stronger joint with the body. I've never broken an arm with this frame although I've crashed it badly a few times ([most](https://www.youtube.com/watch?v=0PPLKe0Yw7w) notable crash, [aut