Use getAssetPath() instead of ASSET_PATH to support broader range of platforms.
Multisampling example determines sample rate from device at runtime.
Move example wrapper code from DemoViewController.mm to dedicated MVKExample.cpp file.
Remove AssImp libraries for iOS and macOS from repo, and add instructions for
generating them from AssImp source files.
Update general README.md file to mention support for iOS and macOS platforms.
Add Apple logo for README.md.
Update Vulkan logo to current registered TM logo.
Update copyright notice of MoltenVK example files to MIT license.
Examples use +/- on main keyboard, instead of numpad.
