This also fixes the unit tests

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

fixes #10501

Conflicts:
	apps/files_external/lib/amazons3.php

folder size and mtime is always unknown in s3

more s3 fixes

make rescanDelay of root dir configurable, add on the fly update of legacy storage ids, !isset -> empty when checking strings

reduce number of http calls on remove and rmdir

fix typo

For some reason the aws-sdk-php package does not caclulate the
signiture correctly when accessing an object in a bucket with a name of
'.'.

When we are at the top of a S3 bucket there is a need(?) to have a directory
name.  Per standard Unix the name picked was '.' (dot or period).  This
choice exercises the aws-sdk bug.

This fix is to add a field to the method to store the name to use instead of
'.' which at this point is hard coded to '<root>'.  We also add a private
function 'cleanKey()' which will test for the '.' name and replace it with
the variable.  Finally all calls to manipulate objects where the path is
not obviously not '.' are processed through cleanKey().

An example where we don't process through clean key would be
	'Key' => $path.'/',

Use correct relationship operator

Per feed back use === instead of ==

use '/' instead of '<root>'

Dependency messages now appear below the configuration options instead of above
Reworked dependency check method to support consolidated messages for multiple backends

Conflicts:
	apps/files_external/lib/google.php
	apps/files_external/lib/swift.php
	apps/files_external/templates/settings.php

Conflicts:
	apps/files_external/lib/amazons3.php
	apps/files_external/lib/swift.php

Fixes #5752

Optional parameters are now really optional

Fixes #5861

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