Receiver plane depth bias for directional shadow

Should anyone want to give it a try, here is Receiver plane depth bias for 4.16. (You need to have linked github account to view.)

The change is partially based on 4.17 PCSS code and is a shader edit only. You do not need to build engine from source to try it.
It is incomplete, but generally should work without major issues.
Spot lights are not working correctly, but you might never notice that. Point lights are unaffected. Lower quality presets need to be replaced with no-bias version though.

It is probably good to enable shader development mode and make backups of two USF files in question before overwriting originals.

I am most likely unable to offer any kind of support on this one. Use at your own risk. Make backups!

There are scenes, that seem to benefit from this kind of bias greatly, but also there are ones, that look worse. As everything here, it is situational.