Test for checking the PCAL9471

Implemented	Hardware tested	Branch	Note
configure input/output	[x]	NA	is tested in all the other tests
set high/low	[x]	main
is high/low?	[x]	pcal-input-test
Sett pullup	[x]	pcal-pullup	Internal pullup 100k, one extern 100k to earth, measure then 3v3/2 = 1.65V by voltage dividing
Sett pulldown	[x]	pcal-pulldown	voltage divider, with 100k to match the internal pulldown. The resistor to vdd, and measure between. same as pullup, just to vdd instead of vss
Sett polarity inversion	[x]	pcal-polarity-inversion	the other pins need to be not floating. Else it will not work propperly