Stock and Flow with units

[neonWhiteout]

May want to make a few more tests.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 65.85366% with 98 lines in your changes are missing coverage. Please review.

Project coverage is 61.20%. Comparing base (7182495) to head (b196953).

:exclamation: Current head b196953 differs from pull request most recent head 113bc7e. Consider uploading reports for the commit 113bc7e to get more accurate results

Files	Patch %	Lines
src/stockflow/StockFlowUnits.jl	56.21%	74 Missing :warning:
src/visualization.jl	0.00%	14 Missing :warning:
src/Syntax.jl	89.79%	10 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #119      +/-   ##
==========================================
+ Coverage   60.69%   61.20%   +0.51%     
==========================================
  Files          10       11       +1     
  Lines        2193     2459     +266     
==========================================
+ Hits         1331     1505     +174     
- Misses        862      954      +92     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[neonWhiteout]

I'd like to change the way StockAndFlowF is mapped to StockAndFlowU; need to figure out how to define mappings between schema categories in Catlab.

[neonWhiteout]

Long, long term, there's gonna be a more complex version of this. One that uses dimensions and requires the units you use be of that dimension. May involve some dimension category.