Fixes https://github.com/owncloud/core/issues/12389

Whenever a file is shared with others or with link, a delete button used
to be visible that triggered a direct deletion.

This button has been removed to avoid accidental deletion from people
who might believe it was an unshare button. Unsharing is still possible
inside the share dropdown.

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.

$file only contains the filename and not the absolute path, that means that files in a subdirectory will not get properly resolved and an empty filesize is returned.

This feature only exists on master.

We don't support direct updates from older ownCloud versions except the previous one therefore this code is unused and can be removed.

This PR removes phpass and migrates to the new Hasher interface.

Please notice that due to https://github.com/owncloud/core/issues/10671 old hashes are not updated but the hashes are backwards compatible so this shouldn't hurt.
Once the sharing classes have a possibility to update the passwords of single shares those methods should be used within the newHash if block.

fixes download issue introduced by #10755

Conflicts:
	apps/files_sharing/public.php

Added namespaces so that JSDoc can find them.
Fixed a few warnings.
Improved some comments.