ENH: epsilonWallFunction - enable low-Re mode to be [de]activated on a

switch

The new lowReCorrection entry can be used to ensure that the low-Re
mode is only applied when its value is on/true, e.g.

    lowReCorrection      on;

When active, the low-Re mode is active when the local y+ is less than
the calculated y+_laminar.  When inactive, the high-Re form is employed
irrespectively of the local y+.

It has a defaulrt value of off/false for backwards compatibility with
OpenFOAM v1706