de language files changed to Nextcloud

Fix translation strings

singleuser.user.php -> nextcloud

changed to nextcloud

nextcloud server

Changed to nextcloud

default.php for nextcloud themes example

changing it to nextcloud

Add postgres to CI

Add "Global Auth" option to external storage

This adds the "Global Auth" option to the external storage implementation, it is basically done by reverting c2c6caee from https://github.com/owncloud/core/pull/22468.

This was taken from owncloud/core which is AGPL licensed. Commited with "icewind@owncloud.com" to keep the license header signature in sync.

![2016-06-21_14-01-06](https://cloud.githubusercontent.com/assets/878997/16228662/9c243136-37b8-11e6-9700-c1076ddb3d17.png)

Show error message if config file is not readable

[master] sync upstream - 21.06.2016

* when the config file is not writable there is a error message shown
* same happens now if the config file is not readable
* fixes #180

replaced ownCloud by Nextcloud in config sample

Fix conversion issues

Password login forbidden hint

Re-add labels for password inputs for usability

no need to mention ownCloud explicitely in the versions and trash bin app

[stable9] Reintroduce HackerOne into CONTRIBUTING.md

Reintroduce HackerOne into CONTRIBUTING.md

Change to phpdoc type for automatic conversion

fix references to ownCloud in the federated files sharing app

Fix references