Massive update documentation for PowerSimulations

[rodrigomha]

Preview PR docs: Not working for now

Massive update on docstrings and markdowns for documentation of PowerSimulations.

I will update the nomenclature to follow the following structure:

• Lowercase letters are used for variables, e.g., p for power.
• Uppercase letters are used for parameters, e.g., C for costs.
• Subscripts are used for indexing, e.g., (\cdot)_t for indexing at time t.
• Superscripts are used for descriptions, e.g., (\cdot)^\text{th} to describe a thermal (th) variable/parameter.
• Bold letters are used for vectors, e.g., \boldsymbol{p} = \{p\}_{1,\dots,24}.

TODO for formulations:

• [x] Introduction to Formulations
• [x] Network formulations
• [x] Thermal Gen formulations
• [x] RenewableGen formulations
• [x] Load formulations
• [x] Branches formulations
• [ ] Services formulations

TODO docs:

• [x] Simulation feedforwards
• [x] Debugging infeasible models
• [ ] Model developer guide: DeviceModel
• [ ] Model developer guide: DecisionModel
• [ ] Subsystem explanations

TODO definitions:

• [x] Feedforward
• [x] Template
• [x] Simulation
• [x] Attributes
• [x] Optimizer/Solver
• [ ] Service Model
• [x] Results vs Realized Results

Feel free to comment if other docs should be added

[github-actions[bot]]

Performance Results

Version	Precompile Time
Main	3.306117011
This Branch	3.412366792

Version	Build Time
Main-Build Time Precompile	49.97515415
Main-Build Time Postcompile	2.359731154
This Branch-Build Time Precompile	54.540582953
This Branch-Build Time Postcompile	2.515036504

Version	Solve Time
Main-Solve Time Precompile	651.675156431
Main-Solve Time Postcompile	639.978951977
This Branch-Solve Time Precompile	391.359268194
This Branch-Solve Time Postcompile	365.7897431

[rodrigomha]

Preview is broken for now, given the requirements of using other branches of PSY and IS

[rodrigomha]

I'm done with this docs for now @jd-lara @claytonpbarrows

[jd-lara]

I think the PR looks good for now for me but I am worried about not catching typos and such we need to review in detail before release