feature/kalman-filter

[djvaron]

First working draft of the Kalman filter capability.

Key updates:

• new run_kf.sh run script
• new scripts in src/kf_scripts/
• imi_preview.py behaves differently if KalmanMode=true
• the usual inversion directory is now an inversion_template directory that gets replicated for individual inversion periods in kf_inversions/period{i}