Enums in Surface from Curves node

Created by: Durman

Problem statement

https://github.com/nortikin/sverchok/blob/a611d3ed8459737d71ae4614d90a6549f7c951fe/nodes/surface/interpolating_surface.py#L29-L37

https://github.com/nortikin/sverchok/blob/a611d3ed8459737d71ae4614d90a6549f7c951fe/nodes/surface/interpolating_surface.py#L45-L54

https://docs.blender.org/api/current/bpy.props.html#bpy.props.EnumProperty

There is a known bug with using a callback, Python must keep a reference to the strings returned by the callback or Blender will misbehave or even crash.

D.node_groups['NodeTree'].nodes['Surface from Curves'].bl_rna.properties['nurbs_implementation'].enum_items <bpy_collection[0], EnumProperty.enum_items> but should be <bpy_collection[1]

Solution is to move items outside of the functions.