Create sftp.php

Adapter for SFTP using the pure php SSH library phpseclib
Update apps/files_external/appinfo/app.php

Adding support for SFTP
Update apps/files_external/lib/config.php

Adding support for SFTP mounts
Update apps/files_external/lib/sftp.php

Added checks for host keys and added exceptions thrown if constructor fails.
Update apps/files_external/lib/sftp.php

Added a little better exception handling, hopefully making it a little more robust
Update apps/files_external/lib/sftp.php

Added copyright notice
Added phpseclib to files_external as 3rdparty
Update apps/files_external/lib/sftp.php

Updated to using local 3rdparty + added a few missed braces.
Update apps/files_external/lib/sftp.php

Created test() function as per @pull/1031
Update lib/filestorage/common.php

Added function to clean a path
Update apps/files_external/lib/sftp.php

Added cleaning the root path
Merge remote-tracking branch 'upstream/master'

Conflicts:
	apps/files_external/lib/config.php
Update lib/filestorage/common.php

Small cleanup
keep track of trash bin size
use never more that 50% of available disc space for the trash bin
Password Toggle Works on Installation as well.
Removed whitespace from installation.php
Fix filelist shifting up one row on (multi)select
Personal Page Password Toggle Also Loads Well.
comment added