Overhaul the PelePhysics docs (currently very out of date and disorganized)

[baperry2]

Overall objective: make the documentation organization match the code organization

• Quickstart/Installation
• Introduction: overview of code functionality and design
• Major source components
  • EOS
  • Transport
  • Reactions
  • Soot
  • Spray
  • Radiation
  • Utility
    • PMF
    • Filter
    • Diagnostics. PR: bool int conversion in DiagFramePlane #573
    • Plt File Management
    • Turbulent inflows (high priority), see Document Turbinflow and Other Utils #401. PR: Move turb inflow helpers from PeleLMeX and add documentation #489
• Mechanisms: provide references
• Support codes
  • CEPTR
  • MechanismPAH
  • Turbulent Inflow
  • PMF Generator
  • liquidProp
• Testing
  • EosEval
  • ReactEval
  • ...