Move \OC\Security to PSR-4

lib/private/Security/CSP/ContentSecurityPolicy.php

lib/private/Security/CSP/ContentSecurityPolicyManager.php

lib/private/Security/CSRF/CsrfToken.php

lib/private/Security/CSRF/CsrfTokenGenerator.php

lib/private/Security/CSRF/CsrfTokenManager.php

lib/private/Security/CSRF/TokenStorage/SessionStorage.php

lib/private/Security/Certificate.php

lib/private/Security/CertificateManager.php

lib/private/Security/CredentialsManager.php

lib/private/Security/Crypto.php

lib/private/Security/Hasher.php

lib/private/Security/SecureRandom.php

lib/private/Security/TrustedDomainHelper.php