Replace EngineBlock_Corto_Filter_Output with an Outgoing response processing pipeline.

[phavekes]

This issue is imported from pivotal - Originaly created at Jan 6, 2016 by Daan van Renterghem

Should functionally be exactly the same.

Blocked by: #111136704

[phavekes]

The implementation has since this issue was created been slightly refactorered to not use opaque by-reference modification of requests/response data. The implementation is now very transparent and we see no need in improving it in the foreseeable future. (Joris Steyn - Mar 2, 2018)

[phavekes]

The ProxyServer still modifies responses/attributes by reference, and we've been bitten by it while fixing a bug on how ARP does not update the attribute types inside the SAML2 library. So this does need some more work! (Joris Steyn - Jun 15, 2018)