M1: device-motion pointing !6

Stacked on !5 (targets m1-widgets).

• SkyRenderer.Pointing: camera direction from the third row of the Core Motion rotation matrix (xTrueNorthZVertical). Four orientation tests.
• App: MotionPointer at 60 Hz with a low-pass filter; header button to follow the phone; a drag hands control back to touch.
• PLAN.org: M1 status.

Compiles for simulator and device (generic/platform=iOS). Not run on a device: the simulator has no motion sensors, so the matrix-row convention is unverified on hardware. swift test: 19 pass.