Eq-mount support under IMU dead-reckoning tracking

[TakKanekoGit]

Work-in-progress...

Features:

• IMU dead-reckoning tracking for EQ mounts.
• PiFinder no longer needs to be placed upright (it can be mounted as any angle as long as the camera points the same way as the scope).
• For altaz mounts, the charts are displayed in horizontal coordinates (Zenith-up) so that alt/az motion will be left/right and up/down. For EQ mounts, the charts are displayed in equatorial coordinates (NCP up) so that az/dec motion will be left/right and up/down.

Changes:

• imu_pi.py: IMU data coordinates are no longer altered here depending on the PiFinder type. IMU outputs will be they are from the IMU. This is now done in imu_dead_reckoning.py.
• integrator.py: Substantial changes. Tracking is done in the equatorial coordinates rather than altaz coordinates. Use quaternion for the IMU dead-reckoning. Sets solver["Roll"] depending on the mount type for chart display.
• pointing_model\: The new classes and functions are grouped up here. It's possible that we could extend this in the future?
• requirements_dev.txt: Requires numpy.quaternion.

This PR touches the core of the IMU functionality so it still needs to be tested thoroughly on all PiFinder types and also on altaz and EQ mounts.

Issues:

• Fix issues after merging with the auto exposure feature
• Chart rotates 180 degrees to the East of Mirfak (from sky testing): Pointings in RA, Dec were OK but in Chart mode, the chart rotated 180 degrees as I crossed to the East of around Mirfak in Perseus with the result that slewing to the
  East showed up as moving to the right.
• Southern hemisphere & equator EQ mode: Should it be South Pole up (roll = 180 deg)?
• Southern hemisphere & equator Alt/az mode: if lat < 0: Display Roll + 180 deg (south up). Use North at equator

Sky test IMU orientations

• Flat v2
• Left
• Right
• Straight
• Flat v3
• as_dream