Use setNeedsUpdate() instead of needsUpdate setter

[dubejf]

For Texture, BufferAttribute, and InterleavedBuffer, introduce new method setNeedsUpdate() instead of the faked property needsUpdate. Replace uses of needsUpdate = true and document the new APi.

Naming: setNeedsUpdate() could be named something like incrementVersion() if you prefer. I don't think update() is appropriate as it doesn't directly perform an update.

Material and uniforms don't have a version counter, They still use the boolean flag needsUpdate (no change).

[mrdoob]

Hmmm... I'll think I'll hold this one for the next cycle.

[threejsworker]

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http://threejsworker.com/viewpullrequest.html#6908