Update documentation

[wbinventor]

This is intended to start a conversation on the various features that have been implemented to the code over the last 6 months and which should be added to the documentation. Some items that come to mind that should be added to the online documentation before the next release include:

User's Guide

• polar quadrature API
• fixed source calculation API
• FSR volume correction API
• adjoint calculations
• plotting centroids, eigenmodes
• periodic boundary conditions

Theory & Methodology

• k-nearest neighbor CMFD updates
• krylov subspace solver
• adjoint solver

[wbinventor]

Added periodic boundary conditions to this list.

[wbinventor]

I compiled a list of updates we need to make to the documentation based on our "All Hands" day last week.

Installation

• Remove deprecated --no-numpy flag
• Add Matplotlib as required dependency

User's Guide

• Polar quadratures
• Fixed source and criticality calculations
• Moderator rings
• Convergence criteria
• k-Nearest Neighbor CMFD
• Periodic boundary conditions
• Change Circle to ZCylinder
• Changes to Material and openmoc.materialize
• Add new capabilities in openmoc.plotter
• Discussion of 3D geometries
• Computing FSR / pin powers
• Adjoint calculations
• SPH factor calculator
• FSR volume correction
• Exponential evaluation options
• Multi-eigenmode Krylov solver

Theory & Methodology

• k-Nearest Neighbor CMFD
• Incorporation of nu-scatter into k-eigenvalue
• SuPerHomogenisation (SPH) factors
• Adjoint calculations
• Multi-eigenmode Krylov solver

Developer's Guide

• Writing documentation
• References