String

- Putting "" into a String will no longer store the terminating null
character in the Vector.
- GetLength and IsEmpty no longer consider the terminating null
character.
String

Added static Compare functions
String
- Unit Tests for operator+= and operator+
String
- Unit Tests for operator== and operator!=
String
- Unit Tests operator>, operator<, operator>=, operator<=
String

Added comment about refactoring for less lines of codes