Partial upgrade to UE 4.19

[trentpolack]

I got the whole thing building properly given the changes made to UE4's codebase and build chain since the last version of this. The upgrade wasn't particularly elegant, but it was a quick stab to get some folks up and running. Minus the running, because:

• There's a shader issue at launch, but I ran out of time to really delve into it; shouldn't be too terribly complex (and likely related to shader format changes since the last version).
• No idea if it actually works at launch after the shaders are fine.

[marynate]

@trentpolack Thanks for the PR. I did some modification base on your PR for both 4.18 and 4.19.
It'll build successfully on 4.18 and 4.19 not working fully yet.