add y to with-aspect naming schema
delete all children's previews when deleting a folder

add phpdoc

Conflicts:
	lib/private/preview.php
Use `/` as redirect location if webroot is set to an empty value

If the webroot has been set to an empty value or ownCloud has been installed at the root location (`/``) there is a fair chance that the redirect for password resets does not work at all.

This means that while the password is getting resetted the user is not redirected to the login page.

I'm aware that it might be better to just set the webroot to `/` in those cases but this patch is better in the regard that it cannot break stuff.

Thanks to @PVince81 for helping me debugging this. (I'm a moron and assumed it couldn't be THAT easy)

Reported by @cdamken
Merge pull request #12373 from owncloud/backport_preview_fixes_stable7

Backport preview fixes stable7
fixes undefined appitem - fixes #12396
The "dir" key is used within the public sharing template to indicate in which directory the user currently is when sharing a directory with subdirectories. This is needed by the JS scripts.

However, when not accessing a directory then "dir" was set to the relative path of the file (from the user's home directory), meaning that for every public shared file the sharee can see the path.
(For example if you share the file "foo.txt" from "finances/topsecret/" the sharee would still see the path "finances/topsecret/" from the shared HTML template)

This is not the excpected behaviour and can be considered a privacy problem, this patch addresses this by setting "dir" to an empty key.

Port of https://github.com/owncloud/core/pull/12262, approved with https://github.com/owncloud/core/pull/12262#issuecomment-64394040
use login name to verify password
Try to read the file only instead of trying to touch

The permissions are already catched properly on the installation so we just have to check whether the file is readable to prevent fatal errors from happening.

Fixes https://github.com/owncloud/core/issues/12135

Conflicts:
	lib/private/config.php
Merge pull request #12415 from owncloud/port-12262

Backport #12262
Merge pull request #12397 from owncloud/fix-undefined-appitem

[stable7] fixes undefined appitem - fixes #12396
fix calculation of expiration date if there is a default expiration date set (but not forced) and the user does not want the link to expire.
Consolidate if statement, and update unit test
Merge branch 'stable7' of https://github.com/owncloud/core into stable7
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