src/vsg source directories

The implementations provided by the src/vsg directories mirror the structure of the include/vsg header directory structure.

• src/vsg/core - core library class implementstion

• src/vsg/nodes - graph node implementations

• src/vsg/traversals - traversal implementations

• src/vsg/vk - Vulkan integration

• src/vsg/vk- Viewer implementations

• src/vsg/utils - Utility implementations

• src/vsg/introspection - Introspection implementations