To avoid conflicts in dependency version, this commit put examples using
different renderers in different crates.
Especially, glium and gfx do not necessarily depend on the same version
of glutin.
We have two examples:
- imgui-examples (main examples, use gfx renderer here)
- imgui-glium-examples (basic hello_glium example + maybe some texture stuff)
Once vulcano support lands, we may add: imgui-vulkano-examples.
This commit currently only moves files around. We plan to use gfx as a
"main2 renderer for now on as gfx is more actively maintained that
glium. Subsequent commits will migrate some glium examples to gfx.
