add additional example - factory schedule MILP

[Crghilardi]

After getting help on this discourse thread, I wanted to submit the finished problem as a 0.19 ready example.

This pull request adds an additional complete MILP example problem.

Notes:

1. I originally wrote this using Cbc. I did not see Cbc listed in the Project.TOML and was not sure what the standards were on solver dependencies in testing, so I changed it to GLPK as other examples

2. This adds 2 data CSV files to the /data folder. Again, didn't want to mess with adding anything so I switched to using DelimitedFiles for reading in data rather than CSV

3. For file naming I just used problemtype_name.jl, not sure if there is a standard. While clicking through the example folder while working through the problem, I thought more explicit names would be helpful FWIW

This has been tested locally with --project=examples run_examples.jl and I get all tests passed on my machine (72/72)

[odow]

Can you copy the structure of the other examples and place everything in a function please? Make sure to add a doctoring to the function describing what the example is and where it is from.

[codecov]

Codecov Report

Merging #1948 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1948   +/-   ##
=======================================
  Coverage   91.17%   91.17%           
=======================================
  Files          33       33           
  Lines        4147     4147           
=======================================
  Hits         3781     3781           
  Misses        366      366

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[codecov]

Codecov Report

Merging #1948 into master will increase coverage by 0.32%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #1948      +/-   ##
=========================================
+ Coverage   91.17%   91.5%   +0.32%     
=========================================
  Files          33      33              
  Lines        4147    4212      +65     
=========================================
+ Hits         3781    3854      +73     
+ Misses        366     358       -8

Impacted Files	Coverage Δ
src/objective.jl	90.9% <0%> (-4.33%)	⬇️
src/quad_expr.jl	92.66% <0%> (-0.54%)	⬇️
src/parse_expr.jl	88.09% <0%> (-0.07%)	⬇️
src/_Derivatives/subexpressions.jl	100% <0%> (ø)	⬆️
src/macros.jl	93.27% <0%> (+0.26%)	⬆️
src/aff_expr.jl	88.54% <0%> (+0.26%)	⬆️
src/parse_nlp.jl	90.72% <0%> (+0.66%)	⬆️
src/nlp.jl	91.93% <0%> (+0.67%)	⬆️
src/operators.jl	86.89% <0%> (+2.9%)	⬆️
src/optimizer_interface.jl	81.81% <0%> (+4.89%)	⬆️

---

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[odow]

Looking good. Just a few minor style comments.

[joaquimg]

production[5, :B] == 0

[Crghilardi]

I have not looked at this in over a year. I am going to close this PR and submit a new one that is properly branched instead of on master (and fix that space issue...). My fork is so far behind I am having trouble getting everything working again XD