This change allows AppFramework applications to specify a custom CSP header for example when the default policy is too strict. Furthermore this allows us to partially migrate away from CSS and allowed eval() in our JavaScript components.

Legacy ownCloud components will still use the previous policy. Application developers can use this as following in their controllers:
```php
$response = new TemplateResponse('activity', 'list', []);
$cspHelper = new ContentSecurityPolicyHelper();
$cspHelper->addAllowedScriptDomain('www.owncloud.org');
$response->addHeader('Content-Security-Policy', $cspHelper->getPolicy());
return $response;
```

Fixes https://github.com/owncloud/core/issues/11857 which is a pre-requisite for https://github.com/owncloud/core/issues/13458 and https://github.com/owncloud/core/issues/11925

Issue/14204 revert #14171

This reverts commit c9b56084.

This reverts commit f6a452ca.

Removed anchor in config.sample.php

Ensure that passed argument is always a string

App install behind a Proxy

Some code paths called the `normalizePath` functionality with types other than a string which resulted in unexpected behaviour.

Thus the function is now manually casting the type to a string and I corrected the usage in list.php as well.

Improve: Index for file_map

Added two indices for file_map, that improve syncing and uploading and deleting files

generate valid human readable text for 0 

Additional controllermethodreflector inheritance tests

catch any whitespaces which might get written to the output buffer while...

Remove internal annotation

PHPStorm complained about those functions being declared as Internal. I doubt that this is actually the case since they are even in the public API.

Disable application-specific favicons for non-user pages

Add .tag file to make tar balls tracable

add timeout to curl request

Added overview of groups a user is member of

Clean-up of messages (orthography, format)

Reuse known fileids and cache data in the scanner

Deprecate `OC_JSON` and `OCP\JSON`

Orthography: "Back-end" -> Backend (without hyphen) and correction of "users" to the genitive "user's"

Added the missing space between value and unit, as it is formatted in all other places across ownCloud.

This deprecates – but not removes – those two classes and all functions in it. There is no reason that new developments should use those methods as with the AppFramework there is a replacement that allows testable code.

With the `@deprecated` annotation IDEs like PHPStorm will point out to the developer that a functionality is deprecated and that there is a better suited replacement.

Remove unused file

This file is unused and has been last modified two years ago. Furthermore it won't evne work anymore properly because it uses things  like `CONFIG_DATEFORMAT` which are gone a long time ago...