Reorganize Directory Layout

[enlight]

Prior to UE 4.8 build output for engine plugins ended up in Engine/Binaries and Engine/Intermediate, as of UE 4.8 build output ends up in the Binaries and Intermediate directories within the individual plugin directories. Also, I believe it's now possible to load third party DLLs from outside the Engine/Binaries directory. At the very least that should allow us to move the Klawr.ClrHost projects into the Klawr runtime plugin directory, eliminating the need to create a directory junction in Engine/Source/ThirdParty, and maybe the need to copy the binaries to the Engine/Binaries directory.