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.)

tests/test_timer.cpp

@@ -33,7 +33,7 @@
 #include <opm/parser/eclipse/Parser/Parser.hpp>
 #include <opm/parser/eclipse/Parser/ParseContext.hpp>
 #include <opm/core/simulator/SimulatorTimer.hpp>
-#include <opm/core/utility/Units.hpp>
+#include <opm/parser/eclipse/Units/Units.hpp>
 
 #include <string>
 #include <iostream>