File system framework improvements

[buskamuza]

• Improve FS API
  • Eliminate duplicated libraries:
    • Deprecation of Magento\Framework\Filesystem\Io
    • Unify Ftp library instead of \Magento\Framework\System\Ftp and \Magento\Framework\Filesystem\Io\Ftp
  • Agree on API convenient for developers. Current API requires extra actions from the developer, and in some cases makes impossible to access files/folders in some context (e.g., it's necessary to create a directory and only then access necessary file).
  • Revisit the security measure limiting accessing files only in specific directory. Find an API that will be convenient and, in the same time, covers security requirements.
• For cloud - do not write to local FS
• API for media files to write to object storage
  • Logs (everything in "var") to be written to remote storage
  • Adapter for switching between local and remote storage
    • Config from env.php
    • Storages: S3
• Builds on environment close to cloud
  • And composer-based
• DevBox close to cloud env

[buskamuza]

Related issue - #111

[diazwatson]

Same applies Magento\Framework\Filesystem\Io\File
there are some methods available in:

Magento\Framework\Filesystem\Io\File

and some others in:

\Magento\Framework\Filesystem\Driver\File

• Before remove I think we should merge them all into one.
• What about 3rd party modules using Magento\Framework\Filesystem\Io?

[buskamuza]

What about 3rd party modules using Magento\Framework\Filesystem\Io?
Everything should be deprecated first.