make matrix mode better defined, pull in Color/Wheel helper functions

[TonyLHansen]

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• Describe the scope of your change--i.e. what the change does and what parts of the code were modified. This will help us understand any risks of integrating the code.

Make matrix mode better defined by defining the strand length to be equivalentl to a 1xN matrix. Allow the matrix sizes to be updated. Allow switching back and forth between treating the pixels as a single strand OR as a matrix. Pull in the Color and Wheel helper functions from the examples as stati functions. In the example code, take advantage of helper functions now being in the Adafruit_WS2801 library.

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I am running code against this changed code. For example, I have a program file that incorporates both of the example code, switching back and forth between using the code in strand mode and in matrix mode.

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