To recreate a swapchain now requires making a new SwapchainBuilder or
keeping the old one around. Removed the recreate function since its
purpose was unclear. Introduced set_old_swapchain to allow recyling the
old swapchain. Updated documentation and getting started guide.
Updated the documentation for using the new <error_code> based errors.
Also fixed an issue where SystemInfo wouldn't check if layers had a
debug_utils extension.
