Add new StringParser type alias
Rename RawStringParser class

The RawStringParser class is going to be replaced by a new
implementation. The old implementation is temporarily kept in a
different name.
Add new RawStringParser class

The most of RawStringParser test cases are removed since they were just
duplicates of the StringParser test cases.
Rename WordComponentParserBase class

The WordComponentParserBase class is going to be replaced by a new
implementation. The old implementation is temporarily kept in a
different name.
Add new WordComponentParserBase abstract class

Some test cases are commented out since some features are not yet
implemented.
Rename WordComponentParser class

The WordComponentParser class is going to be replaced by a new
implementation. The old implementation is temporarily kept in a
different name.
Add new WordComponentParser class
Rename WordParser class

The WordParser class is going to be replaced by a new implementation.
The old implementation is temporarily kept in a different name.
Add new WordParser type alias
Rename AssignmentParserBase class

The AssignmentParserBase class is going to be replaced by a new
implementation. The old implementation is temporarily kept in a
different name.