extract major openfoam version from WM_PROJECT_VERSION environment
variable in make/options files and use it for a preprocessor flag
(OPENFOAM_VERSION_MAJOR) for conditional compilation
make CFDEMcoupling compile with OF 4.x, 5.x and 6
MULES and CMULES have been extended so that the limits can be supplied
as fields. These arguments are templated so that zeroField, oneField or
UniformField<scalar> can be used in place of a scalar value with no
additional overhead.