Moves the 256 entry GAMMA table into pimoroni_common.
Should probably be added into a library so MicroPython is built with only one instance of the table.
This covers an edge case where pixels are updated intermittently - such as the once that happens when clearing before a Python soft reset.
Under normal circumstances users should `start` the LED strip and allow it to continuously update.
Adds an ifdef guard around `pio_sm_unclaim` that prevents it being called when MicroPython cleans up/finalizes classes.
For some reason this appeared to be causing a hardfault.
Phil Howard
ZodiusInfuser