Fix spirit level when screen rotated

[matijatosic]

Take default rotation/reflection into account, as defined via the Settings app.

[thyttan]

Thanks - I'll take a look and be back!

[thyttan]

Looking good!

I just have one hold up. Maybe the firmware should take care of rotating the accelerometer readings before passing it on instead, @gfwilliams? Adjacent previous discussion:

Another note: If implemented, would this mess with accelerometer readings?

Right now they are left as-is. I guess it depends what you intended to use the readings for. Step counting/etc would work fine.

Originally posted by @gfwilliams in #1040 (comment)

PRO re rotating in firmware:

• apps don't have to add code to handle rotation.
• I guess it should be faster to do the rotation in firmware.

CON re rotating in firmware:

• adds some overhead for the, I guess overwhelmingly, most common case of not rotating the screen when checking the rotation setting.
• increases firmware size (negligibly I'd think).

[gfwilliams]

Yes, I think you're right - we should probably do that in firmware. The hit itself should be minimal, and we do it for touchscreen and I think even accelerometer 'tap' events already.

It's hard to think of any apps that wouldn't benefit from it being flipped - the only one I can think of that uses accelerometer right now is ball maze, but I guess that would be broken at the moment if done on a rotated screen

[gfwilliams]

Just done :)