Blender Git Loki

Layers - initial commit

This is mostly DNA + doversion and some util functions.
I need to look at the layer-manager branch to see how
Julian Eisel (Severin) managed to handle nested lists
(required for collections).

Also, since I think doversioning may get more complex as the project
evolves, I started the vesioning_280.c file.

And the changes in readfile.c were so that I could include into the
versioning_280.c file only the DNA_* that were really needed.

(if someone feels like doing a cleanup, I'm sure the other
versioning_*.c files could use the same treatment)