[Bf-cycles] Script node updating from OSL defaults

[Lukas Tönne]

> But how about adding an explicit "reset to defaults" button? That way
> one could quickly test the OSL parameter defaults without destroying a
> carefully set up scene.

One more thought: In the long run the OSL parameter defaults should be
translated to RNA property defaults (that currently does not work due
to the generic socket properties). When that is implemented the "reset
to defaults" button could be a general feature for all nodes, just as
a shortcut so users don't have to reset each socket value
individually.