Allocators only complicated the interface and likely aren't needed. They
are useful on other function calls, but none of the ones here mattered.
A constructor was added to swapchain that has all the handles it needs.
This way users don't have to pass in the vkb::Device struct to use the
swapchain builder
Before it only had 1 priority even if there were multiple queues.
Now it creates a vector of priorities so it shouldn't cause issues.
It also means logic to setup actual priority values can be put in place
in the future
Now there is a concise example of the library in use all the way to presenting.
Needs to be rewritten to remove exceptions, but for first pass its good enough.
