Add RATE_CALC_METHOD

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Add a Rate_Calc_Method to the symbol table via initialState and migrate.

Allow two choices:

• Geometric Rate Calculation
  • OD_Free (Indep)
  • Wire_Dia (Indep)
  • L_Free (Indep)
  • Coils_T (Indep)
• Force-Deflection Rate Calculation
  • Force_1 (Indep)
  • Force_2 (Indep)
  • Defect_1 (Dep <-> Indep)
  • Defect_2 (Dep <-> Indep)

Switch model between the two by varying Independent to Dependent Variables, and back. Default is Geometric Rate Calculation. Add in if-statement to eqnset to select between the two choices.

[1fifoto]

Uses a simplified 'shadow' symbol table, called 'st', consisting of a single simple array of values instead of two: a 'p' array and an 'x' array. This allows the Deflect_1 and Deflect_2 to switch from dependent to independent variables. See #717

[1fifoto]

See #796.