Refactor Buffer Handle Specifications

[SpinnerX]

This PR resolves #34

Changelogs

• Changed .write to .transfer for clarity in performing data transfers for GPU access.
• Explicit size of bytes to the buffer_stream handles.
• Explicit vertices and indices to vk::vertex_buffer and vk::index_buffer.
• Explicit API specification for setting filepath for vk::texture.
• Added as_bytes<T> utility function.
• Added to_bytes<T> utility function.
• Fixed additional logic for vk::texture to loading image data.
• Additional code cleanup.