this fixes some annoying inconsistencies (e.g., the recently
introduced 'dyne' unit was unavailable in the opm-core version) and
gets rid of some compiler abiguity errors if 'using namespace
Opm::details' was used by code inside the 'Opm' namespace.
Since opm-parser is a hard dependency of opm-core, the only measure
which must be taken by higher-level code is to include
'opm/parser/eclipse/Units/Units.hpp' instead of
'opm/parser/eclipse/Units/ConversionFactors.hpp' or
'opm/core/utility/Units.hpp'.
Note that a potentially better location for this code would be
opm-common, but this would break the Windows build of opm-parser.
a8b6047b1d