[WIP] AgentPopulation

[alanlujan91]

Please ensure your pull request adheres to the following guidelines:

• Tests for new functionality/models or Tests to reproduce the bug-fix in code.
• Updated documentation of features that add new functionality.
• Update CHANGELOG.md with major/minor changes.

[codecov-commenter]

Codecov Report

Patch coverage: 76.92% and project coverage change: +0.04 🎉

Comparison is base (9167a76) 73.31% compared to head (620d3c3) 73.35%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1237      +/-   ##
==========================================
+ Coverage   73.31%   73.35%   +0.04%     
==========================================
  Files          76       76              
  Lines       12551    12705     +154     
==========================================
+ Hits         9202     9320     +118     
- Misses       3349     3385      +36     

Impacted Files	Coverage Δ
HARK/core.py	88.40% <73.13%> (-4.92%)	⬇️
HARK/tests/test_core.py	100.00% <100.00%> (ø)

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[llorracc]

Maybe distribution_type_index and distribution_type_discrete_timevarying?

The people at Wolfram have thought long and hard about all of this stuff and have a nice schema for specializing generic distributions to specific cases in Mathematica.