3.6.0b3

Added

• Added optional calibrated=True parameter to acceleration() and up() and
  angular_velocity() and rotation methods of the IMU (support#943).
• Implemented hub.imu.orientation() to give the rotation matrix of the hub or
  robot with respect to the inertial frame.
• Added calibration parameters that can be set for angular velocity offset and
  scale and acceleration offset and scale.
• Added hub.system.reset_storage to restore storage and settings to default
  state.

Changed

• Enabled UTF-8 support for str objects.
• The method DriveBase.angle() now returns a float (support#1844). This
  makes it properly equivalent to hub.imu.heading.
• Re-implemented tilt using the gyro data by default. Pure accelerometer tilt
  can still be obtained with hub.imu.tilt(use_gyro=False).
• Re-implemented hub.imu.heading() to use optionally use the projection of 3D
  orientation to improve performance when the hub is lifted off the ground.
  The 1D-based heading remains the default for now.
• Change return value of connected() property from bool to int using the value
  of pbdrv_usb_get_bcd(). This will allow pro users to be able to tell if they
  have a "nonstandard" charger that could prevent proper
  charging (pybricks-micropython#274).
• When the Bluetooth button is selected to stop the program, don't disable the
  stop button while the hub menu is active (support#1975).

Fixed

• Fixed battery charging timeout if it didn't reach 100% after about 6 hours.
  This is same behavior observed in official firmware. (pybricks-micropython#292).
• Fixed inconsistent battery level reported to user. Now it uses the same value
  as used by the light indicator (support#2055).
• Fixed DriveBase.angle() getting an incorrectly rounded gyro value, which
  could cause turn(360) to be off by a degree (support#1844).
• Fixed hub silently ignoring non-orthogonal base axis when it should raise.
• Fixed not handling negative duration in Speaker.beep() (support#1996).

Removed

• Removed ev3dev and ev3rt-based CI builds. Pybricks 2.0 on ev3dev will
  continue to be available as a separate download.