Allow RGB values to be read from AddressableLEDBuffers without allocating Color objects

[SamCarlberg]

If I want to iterate over a buffer to read or copy data, I currently have to use a pattern like this:

for (int i = 0; i < buffer.getLength(); i++) {
  Color c = buffer.getLED(i);
}

This results in an object allocation for each LED in the buffer. If this code has to run periodically then this can easily result in thousands of new objects per second, even for lower density LED strips like 60/meter - 60 LEDs * 1 object/LED * 50Hz = 3000 objects/sec.

Let's add methods to read the individual R, G, and B channel values directly. A functional-style iterator method would be nice to have to avoid unnecessary indexed for-loops

public int getRed(int index)
public int getGreen(int index)
public int getBlue(int index)

// functional iteration
interface Iterator {
  void accept(int index, int r, int g, int b);
}

public void forEach(Iterator iterator) {
  for (int i = 0; i < getLength(); i++) {
    iterator.accept(i, getRed(i), getGreen(i), getBlue(i));
  }
}