Optimize nodes deduplication routines
Optimize nodes deduplication routines

The idea is to have separate sets per node name in order to speed up the
comparison process. This will use a bit more memory and slow down simple
shaders, but this extra memory is not so much huge and time penalty is
not really measurable (at least from initial tests).

This saves orders of magnitude seconds when de-duplicating 17K nodes and
overall process now takes 0.01sec on my laptop,

tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird