Update to latest dependency libraries for Vulkan SDK 1.1.92.
Generate Hologram demo dispatch files in fetchDependencies and remove them from git.
Update MoltenVK version to 1.0.27.
Update What's New document.
Remove linking MoltenVKSPIRVToMSLConverter from Build Phase in favour of PreLink.
Update to Vulkan header 1.1.83.
Update to latest version of library dependencies.
fetchDependencies script now in top directory to avoid Travis caching of
External directory. fetchDependencies is now smart about fetching vs cloning
and building only what is necessary.