Blender Git Loki

Rename: "Nodes" modifier to "Empty"

This introduces a regression. Users need to re-create their modifiers
and set their values again. The NodeGroups are intact so all they need
is to create new "Empty" modifiers and set the node group.

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Original problem: Eventually most modifiers will be node-based, so naming
this new modifier "Nodes" will get outdated pretty quickly.

Calling it "Empty" it's fairly descriptive, since the node tree simply connects
the modifier Input to an Output, without any effect.

There is a potential problem, that it could be associated with the
Empty object type. Like some sort of Hook.

This is the task T82700, and the design task T82537.