New refactor branch

@nortikin
This is a pull request so I can merge it in a new refactor branch.
I didn't want to merge it straight to master as some bugs are expected.
This is work in progress...
Of note upgrading from within blender doesn't work
It is up to date, all the commits have been merged,
Remark : the addon folder is not the root folder anymore, but the sverchok subfolder.

At this point, some testing by all is welcomed

@wclyffe