Allows people to use Swapchain Builder withtout holding onto the vkb::Device
handle. Also made patch levels optional since they generally don't matter.
Make vk-bootstrap capable of loading the vulkan runtime and not need to
link against the library. This improves the usability of vk-bootstrap since
now you don't need the vulkan library on your system to build.
This commit also changes how SystemInfo works so as to allow the dynamic
vulkan loading.
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.
