Rpi-ws281x

* Fix: Added support for Pi 4 Rev 1.2 - 0xa03112, 0xb03112, 0xc03112

* Fix: Fixed Slice support when setting pixels
* New: Added support for Revision 0xa02083
* New: Added support for Revision 0xa22083

* Fix: Added white colour channel to Color()

This release adds support for the Raspberry Pi 4.

This breaking release drops the "neopixel" (an Adafruit trademark) package from this library so that Adafruit can re-purpose it for their own projects. See 8.

Don't worry- this was just a legacy compatibility shim and you can substitute `import neopixel` for `import rpi_ws281x` and everything will continue to work. There are no functional changes in this release.

Sorry for any inconvenience this might cause your project- if you're using `import neopixel`, since there are no bug fixes or improvements, you may continue to use v3.1.0 until you are ready to migrate.

This release aims to bring feature parity with the legacy Python library shipped with rpi_ws281x and eventually replace it.

* New: Exposed all contents of ws for easy access to strip_type constants
* Fix: Matched functionality of upstream legacy library by supporting strip_type
* Note: Default strip type is WS2811_STRIP_GRB