Add CHI_D; some minor changes for publication

• Add energy binning through CHI_D for energy distribution of neutrons resulting from delayed production
• Change some chained if-else to switch-case statements
• Make NtAction compatible with new block restrictions in MOOSE
• Perform Picard iterations with coupled neutronics and temperature (no delayed precursors)
  • Solve does not converge
  • Full coupling (single matrix) required to converge such tightly coupled physics

3D steady-state and 2D transient capabilities

This update adds capabilities and inputs for:

• 3D steady state
• 2D loss of secondary cooling transient
• 2D loss of flow transient
• 2D control rod ejection transient
• 2D > 2 group calculations

Initial Moltres release

Functionality included in the initial Moltres release is fully-coupled simulation of multi-group neutrons, temperature, and drifting precursors in 2D-axisymmetric models of Molten Salt Reactors. Kernels and boundary conditions are dimension agnostic and can be run for 1, 2, and 3 dimensions. However, computationally efficient simulation of 3D geometries has yet to be demonstrated.