Add support for getting the real client IP behind proxies

Fixes https://github.com/owncloud/core/issues/10624

Fix copy paste fail

Add unittest for comma separated headers

Revert 3rdparty
Make Entity properties ```protected``` as in docs

Entity properties are marked as ```protected``` to correctly reflect the
documentation.

See also owncloud/documentation@644f2eedac8e912c3019366b29ecdfbd9a15c5d9
Merge pull request #10666 from ogasser/appframework_db_tests

Make Entity properties ```protected``` as in docs
Merge pull request #10653 from owncloud/x-forwarded-for

Add support for getting the real client IP behind proxies
Escape error messages
[tx-robot] updated from transifex
Merge pull request #10670 from owncloud/encodeExceptions

Escape error messages