Suggestions for code style improvement

[jquorning]

I have reviewed your work and have some suggestions for improvement. I would say that String can replace Unbounded_String in just about all cases.

1. Use Ada.Containers.Indefinite_Vectors/Ordered_Maps/Holders instantiated with String instead of Unbounded_String vectors and maps.
2. Introduce types for vector Index_Type like Line_Number etc instead of Positive.
3. subtype String_Vector is String_Vectors.Vector etc just after container instantiation. This will make the code shorter and lighter.
4. Use String parameters instead of Unbounded_String.
5. Add typing with types or/and subtypes like Directory_Name / File_Name / Program_Line from String.
6. Use subtype nearly like an alias of common datatypes in packages using them. Ie subtype String_Vector is SP.Strings.String_Vectors.Vector in packages using a lot of String_Vectors.Vector.

I hope the suggestions can be used. Exited to get a macOS version soon..;-)