ENH: Multiple updates to function objects

Updated objects
- corrected Peclet number for compressible cases
- propagated log flag and resultName across objects

New function objects
- new fluxSummary:
  - calculates positive, negative, absolute and net flux across face
    zones
- new runTimeControl
  - abort the calculation when a user-defined metric is achieved.
    Available options include:
    - average value remains unchanged wrt a given threshold
    - equation initial residual exceeds a threshold - useful to abort
      diverging cases
    - equation max iterations exceeds a threshold - useful to abort
      diverging cases
    - min/max of a function object value
    - min time step exceeds a threshold - useful to abort diverging
      cases
- new valueAverage:
  - average singular values from other function objects, e.g. Cd, Cl and
    Cm from the forceCoeffs function object