The SFTP backend now supports public key authentication alongside
password authentication.

Explicitly clear the stat cache after deleting an empty folder to make
sure it is properly detected as deleted in subsequent requests.

This works around a problem with phpseclib where the folder is properly
deleted remotely but the stat cache was not updated.

Remove port from SFTP storage id if it is 22.
This will prevent recreating a different storage entry due to id
mismatch after upgrade.

This reverts commit 6a1a4880.

My IDE was crying...

Introduced with https://github.com/owncloud/core/commit/1df8a5a774ae5d665849daf74540d967826d5e11 in February 2013…

Add support for external files accessed via SFTP using public key exchange authentication.
Keys are generated automatically when the configuration is added, or can be regenerated on demand if a key is compromised.
Creation of a new configuration row now triggers focus on that row. This is used to trigger auto-configuration for SFTP keys.
Generated public keys are saved in user's data directory for easy retrieval by an external application.
Add controller for SFTP key generation AJAX
SFTP class initialisation no longer produces a warning if the password field is missing.
Add unit tests for SFTP with key authentication backend

Fixed the following external storages to not connect in the constructor,
but do it on-demand when getConnection() is called.
- S3
- SWIFT
- SFTP

rename class Crypt_Blowfish to Legacy_Crypt_Blowfish

- Upgraded phpseclib to master version (post 0.3.5)
- Now using fopen() on sftp URL for both read and write
- Fixes #4063

Also adjusted all ext storage backends to not override these when the
default behavior is expected.

When this is the case only the configured max upload size is taking into account for uploading