This results in less merge conflicts when using the
Text Editor > Files > Trim Trailing Whitespace editor setting.
.ptex, .mmg and .json files generated weren't modified
as these are saved by Material Maker. These files could be made
to end with a newline automatically on save in a future commit.
Moved handling of the "global" definitions of shaders into main shader generation code.
Added group creation (does not create inputs yet, and remotes should be cleaned).
updated all preview meshes (to fix problems with depth).
