Added struct ParseMode to control parse behaviour.

- Introduce a very simple class ParseMode which will become a simple
   value object which can be used to control the behavior when errors
   and inconsistencies are encountered in the parse and EclipseState
   construction phases.

 - Added ParseMode instance as second argument to all parseXXX()
   methods.

opm/parser/eclipse/EclipseState/IOConfig/tests/IOConfigTest.cpp

@@ -24,6 +24,7 @@
 #include <boost/test/unit_test.hpp>
 
 #include <opm/parser/eclipse/Parser/Parser.hpp>
+#include <opm/parser/eclipse/Parser/ParseMode.hpp>
 #include <opm/parser/eclipse/EclipseState/EclipseState.hpp>
 #include <opm/parser/eclipse/EclipseState/IOConfig/IOConfig.hpp>
 
@@ -82,7 +83,7 @@ const std::string& deckStr4 =  "RUNSPEC\n"
 
 static DeckPtr createDeck(const std::string& input) {
     Opm::Parser parser;
-    return parser.parseString(input);
+    return parser.parseString(input, Opm::ParseMode());
 }