File base class

Similar to Print, Stream, Client, Server... we probably need a File base class.

Currently File is defined in the SD library, and also in the Bridge library for Yun. Most programs in the Arduino ecosystem which use files are tied to the SD library. Because they include SD.h in their headers, the SD library is automatically brought into the project.

But the SD library isn't the only possible source for files. Flash chips, USB mass storage, network filesystems can also provide files. Without a base class, each library using files needs to be edited.

Use of alternate SD card libraries, like SdFat, is also very difficult without a base class because so many libraries which consume files are SD.h included by their code.

Hopefully the time has come to move File out of the SD library and into an abstract base class?

Lee las definiciones existentes de File en las bibliotecas SD y Bridge y, a continuación, compara las clases base relacionadas Print, Stream, Client y Server. Define la API compartida y verifica que las bibliotecas que proporcionan archivos puedan usarla sin que los consumidores incluyan SD.h; el issue no nombra ninguna prueba ni ningún punto de entrada específico.

Escrito por el modelo de indexación a partir del texto del issue.