Show warning when invalid user was passed

Sometimes there are bugs that cause setupFS() to be called for
non-existing users. Instead of failing hard and breaking the instance,
this fix simply logs a warning.
Remove phpass and migrate to new Hasher interface

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.
Warn for password reset when files_encryption is enabled

This patch wil warn the user of the consequences when resetting the password and requires checking a checkbox (as we had in the past) to reset a password.

Furthermore I updated the code to use our new classes and added some unit tests for it :dancers:

Fixes https://github.com/owncloud/core/issues/11438
Fix scrutinizer issues
Remove uneeded import
Use correct route instead

THX @schiesbn
(I should setup a mail server on my local system...)
Add "postPasswordReset" hook
add password as parameter to the signal so that the encryption can create a new key-pair
listen to the post_passwordReset hook, backup the old keys and create a new key pair for the user
Hide submit button after password change

Creating a new key pair can take 1-2 seconds. So it could happen that the user click the "Reset password" button again which can lead to many nasty things, e.g. we could create two new key pairs in parallel.
fix unreadable label in warning box
Show spinner
Check if the size field is available

In some cases the 'size' field is not available resulting in some PHP errors such as:

```json
{"reqId":"03548fd9e3d3aca15a5796b3b35d7b9d","remoteAddr":"::1","app":"PHP","message":"Undefined index: size at \/Users\/lreschke\/Programming\/core\/lib\/private\/files\/fileinfo.php#125","level":3,"time":"2014-11-17T21:38:57+00:00"}
```

This can be experienced when creating a new empty file and deleting it right away, then when going to the trash bin this error is thrown.
center spinner
make sure that we don't find the wrong shares if a user and a group have the same ID
make sure that we only find the shares from the correct share type if users and groups with the same ID exists
use the new base class for unit tests
only users can have a display name different from the id
Added function to load translations from JS

For apps that support async translation loading, a new function
OC.L10N.load() can be used to asynchronously load the translations
for a given app.
Fix type hinting for app manager