Refactor initial parsing stage

- Reduced the amount of state in the RawKeyword and ParserState classes.
 - RawKeyword class has normal constructor - remove init method.
 - The Rawxxx symbols are module private and the header files are not installed.
 - Removed several unused static methods from Rawxxx and ParserKeyword.

tests/parser/DeckTests.cpp

@@ -32,7 +32,8 @@
 #include <opm/parser/eclipse/Parser/ParseContext.hpp>
 #include <opm/parser/eclipse/Parser/ParserItem.hpp>
 #include <opm/parser/eclipse/Parser/ParserRecord.hpp>
-#include <opm/parser/eclipse/RawDeck/RawRecord.hpp>
+
+#include "src/opm/parser/eclipse/Parser/raw/RawRecord.hpp"
 
 using namespace Opm;