Refactored the Vulkan::Image class

Refactored the Vulkan::Image class

> Removed the PIMPL pattern.
> Renamed the static method New that created a RefCountedImage from an external Vulkan image handle to NewFromExternal.
> Removed the Vk prefix from certain getter methods in the Vulkan::Image class.
> Moved the image creation login to the Vulkan::Graphics class.
> Moved the image memory binding logic to the Vulkan::Graphics class.
> Renamed the BindMemory method of the Vulkan::Image class to AssingMemory.
> AssignMemory now only assigns the RefCountedGpuMemoryBlock to the image to increase the ref count. To bind memory to an image, users should use the Graphics::BindImageMemory(<image>, <memory>, <offset>) method.
> Altered already existing image creation code to use the new paradigm.

Change-Id: I32bd621dcd59eac7c24a0759798bde15a7870083