BUG: add switch for nu:DphitEff in kEpsilonPhitF (fixes #1560)

Including nu in DphitEff even though it is not present in (LUU:Eq. 17) provided higher level of resemblance to benchmarks for the tests considered, particularly for the peak skin friction (yet, pressure-related predictions were unaffected). Users can switch off nu in DphitEff by using includeNu entry in kEpsilonPhitFCoeffs in order tofollow the reference paper thereat. includeNu is left true by default. See GitLab issue #1560 (closed),

• removes redundant phit() and f() access funcs,
• replaces dimensionedScalar with dimScalar to gain space.

LUU: Laurence, D. R., Uribe, J. C., & Utyuzhnikov, S. V. (2005).