Feature/better imm filter

[EirikKolas]

IMM filter with support for models of different state-sizes

I used a lot of variadic templates and integer sequences to make the user interface easy to use but it does make the code a bit hard to understand. Please comment if something is unclear

[codecov]

Codecov Report

Merging #8 (6910e08) into main (a7f4ce0) will increase coverage by 0.60%.
The diff coverage is 32.42%.

❗ Current head 6910e08 differs from pull request most recent head 6069744. Consider uploading reports for the commit 6069744 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #8      +/-   ##
==========================================
+ Coverage   31.36%   31.96%   +0.60%     
==========================================
  Files          24       26       +2     
  Lines         880     1098     +218     
  Branches      617      760     +143     
==========================================
+ Hits          276      351      +75     
- Misses         31       43      +12     
- Partials      573      704     +131     

Flag	Coverage Δ
unittests	31.96% <32.42%> (+0.60%)	⬆️

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