consolidate the unit system to opm-parser

since the unit code within opm-parser is now a drop-in replacement,
this simplifies things and make them less error-prone.

unfortunately, this requires quite a few PRs. (most are pretty
trivial, though.)

examples/compute_tof.cpp

@@ -30,7 +30,7 @@
 #include <opm/common/ErrorMacros.hpp>
 #include <opm/core/utility/SparseTable.hpp>
 #include <opm/core/utility/StopWatch.hpp>
-#include <opm/core/utility/Units.hpp>
+#include <opm/parser/eclipse/Units/Units.hpp>
 #include <opm/core/utility/miscUtilities.hpp>
 #include <opm/core/utility/parameters/ParameterGroup.hpp>