Improvements for Planar reflections.

[anonymous_user_fbe2d247]

@Daedalus51

I dont have anything to add besides horizontal blur options XD But nevertheless…THIS IS AWESOME! Thank you so much man! I think these are great and important optimizations

-Daedalus

I forget to add this pull request.
https://github.com/EpicGames/UnrealEngine/pull/4553
Vertical blur skips every other pixel which cause visible streaks.