Implement unit normalization

[bgyori]

This PR implements an approach to normalize any unit in a model that represents an absolute count of something (e.g., population).

todo

• Add endpoint consuming mira template model
• Add endpoint consuming AskePetriNet JSON

[codecov-commenter]

Codecov Report

Merging #194 (8c7bb65) into main (a499579) will increase coverage by 0.71%.
The diff coverage is 99.02%.

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@@            Coverage Diff             @@
##             main     #194      +/-   ##
==========================================
+ Coverage   76.55%   77.27%   +0.71%     
==========================================
  Files          65       66       +1     
  Lines        5068     5228     +160     
==========================================
+ Hits         3880     4040     +160     
  Misses       1188     1188              

Impacted Files	Coverage Δ
mira/metamodel/utils.py	91.66% <93.75%> (+4.16%)	⬆️
mira/metamodel/template_model.py	62.36% <94.73%> (+1.96%)	⬆️
mira/dkg/model.py	96.34% <100.00%> (+0.31%)	⬆️
mira/examples/sir.py	100.00% <100.00%> (ø)
mira/metamodel/__init__.py	100.00% <100.00%> (ø)
mira/metamodel/ops.py	79.88% <100.00%> (+3.65%)	⬆️
mira/metamodel/templates.py	85.18% <100.00%> (-0.39%)	⬇️
mira/metamodel/units.py	100.00% <100.00%> (ø)
mira/modeling/askenet/petrinet.py	96.31% <100.00%> (+0.61%)	⬆️
mira/sources/askenet/petrinet.py	91.30% <100.00%> (+0.07%)	⬆️
... and 2 more

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[kkaris]

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