* Both paths still exist in code during this transition. The GetDynamicMeshElements path is currently disabled, enable with 'r.UseGetDynamicMeshElements 1'.
* DrawDynamicElements was called once per pass, all sorts of pass-specific cruft had leaked in along with short-term modifications of shared structures (vertex factories and material proxies). DrawDynamicElements was not const, so a bunch of 'update' type work had leaked in. Various PreRenderView implementations relied on the view being in the view family.
* GetDynamicMeshElements is called once in InitViews, and the resulting meshes are used in various passes. GetDynamicMeshElements is const and must not modify the proxy, update work should be pushed to the proxy from the game thread. GetDynamicMeshElements can be called on views that are not in the view family, which allows a proper view for shadow depth passes.
* View mode override functionality moved out of the individual proxies into a centralized place, ApplyViewModeOverrides
* GPU particles not working yet, FRecastRenderingSceneProxy not implemented
[CL 2253795 by Daniel Wright in Main branch]
Add Runtime/Engine/Private as and Engine private include path
Rename Engine/Private/Materials/MaterialInstance.h to MaterialInstanceSupport.h because it was causing ambiguities
Move cpp files from Classes and Public into Private
#codereview steve.robb, Robert.Manuszewski, nick.penwarden
[CL 2078806 by James Golding in Main branch]
