Added -chunkinstalldirectory and -chunkinstallversion to UAT commandline options.
Added Chunk Dependency Graph for use with -manifests.
HTTPChunkInstaller correctly re-uses old builds to reduce download sizes.
ChunkInstaller delegates correctly use delegate handles.
Windows uses HTTPChunkInstaller by default if enabled in project Build.cs.
Switched HTTPChunkInstaller tasks to threads.
[CL 2499607 by James Moran in Main branch]