Renaming withCredentials Field to crossOrigin
CORS switch for all three cases
No given value as standard for crossOrigin
"Intelligent" selection of CORS-Behaviour

If the requested image resource for textures is forbidden by SOP,
automatically add CORS-Headers.
Fix overlooked change in X3DTextureNode-Attribute "crossOrigin"
Fix comments for better understanding
Merge pull request #415 from Sharian/CORSfix406

CORS fix #406