Enhance cookbook extended filename section

Summary

Move and update the section about extended filename with examples.

Rationale

Extended filename is very interesting features of OTB and not only of OTB-Applications. Therefore put it in a dedicated file which can be extended with new examples seems for me a good idea.

Implementation Details

Classes and files

Add a ExtendedFilenames.rst file and remove this part from the OTB-Applications.rst file

Additional notes

It could be useful for users to have more examples.