Fixed inputs of absolute, accumulate and add plugins.
Introduced a few basic renderer-scoped default values that can be referenced by slot declarations to keep redundant object allocation down.
Updated the array generator to emit 'null' when the size equals 0 or when no size is supplied.
Fixed inputs of the alpha modulator.
Fixed the inputs of the clamped accumulate, clamp, color add, color blend, color display and color multiply plugins.
Fixed the inputs of the matrix concatenate plugin and removed a redundant connection_changed() implementation.
Fixed the inputs of the convert bool > float, camera > matrices, color > hsla, color > rgba, float > bool, hsla > color, matrices > camera, oscillator > unit, rgba > color, vector > xyz and cosine plugins.