created skeleton for a Kalman filter

[JSMTHWCK]

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.75%. Comparing base (ee40200) to head (8352e4d).
⚠️ Report is 2 commits behind head on development.

Files with missing lines	Patch %	Lines
endaq/calc/kalman.py	0.00%	28 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #237      +/-   ##
===============================================
- Coverage        71.41%   70.75%   -0.66%     
===============================================
  Files               35       36       +1     
  Lines             3278     3307      +29     
===============================================
- Hits              2341     2340       -1     
- Misses             937      967      +30     

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