Add Accumulated State Densities with out of sequence measurements

[jogehl]

This branch adds a simple implementation of Accumulated State Densities. They can be used not only for in sequence, but also for the out of sequence case.

[sdhiscocks]

@jogehl Would it be possible to provide an example of ASD in action as part of the documentation. Maybe just adapting one of the existing tutorials or examples, but putting the detections out of sequence?

If you haven't already, you'll need to install the documentation dependencies for Stone Soup which you can find in the README (or can be done easily from the base directory with python -m pip install -e .[dev]). Then from base of the repo run python -m sphinx docs/source docs/build. This will build the documentation and execute the examples, outputting documentation into the docs/build/ directory.

[codecov[bot]]

Codecov Report

Merging #309 into master will increase coverage by 0.31%. The diff coverage is 91.50%.

@@            Coverage Diff             @@
##           master     #309      +/-   ##
==========================================
+ Coverage   93.61%   93.93%   +0.31%     
==========================================
  Files         109      126      +17     
  Lines        3665     5307    +1642     
  Branches      528      753     +225     
==========================================
+ Hits         3431     4985    +1554     
- Misses        153      227      +74     
- Partials       81       95      +14     

Flag	Coverage Δ
#integration	71.96% <69.47%> (?)
#unittests	90.37% <83.39%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
stonesoup/metricgenerator/tracktotruthmetrics.py	93.13% <ø> (+1.96%)	:arrow_up:
stonesoup/sensor/radar/radar.py	95.42% <ø> (-0.41%)	:arrow_down:
stonesoup/sensor/sensor.py	100.00% <ø> (ø)
stonesoup/serialise.py	99.29% <ø> (+2.66%)	:arrow_up:
stonesoup/simulator/platform.py	100.00% <ø> (ø)
stonesoup/simulator/simple.py	97.47% <ø> (-2.53%)	:arrow_down:
stonesoup/simulator/transition.py	95.39% <ø> (ø)
stonesoup/smoother/base.py	100.00% <ø> (ø)
stonesoup/smoother/lineargaussian.py	82.92% <ø> (-9.94%)	:arrow_down:
stonesoup/tracker/pointprocess.py	98.36% <ø> (ø)
... and 132 more

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[oharrald-Dstl]

Prior to merging, could commit messages be reworded to give context please?

[sdhiscocks]

Apologies on the delay reviewing and merging this @jogehl. I've opened #734 with minor changes and updating code to work with latest version of the main code base.

[sdhiscocks]

Resolved in #734