Sampled digital inputs rate is slightly incorrect

[jonnew]

A known bug in the breakout_digital_device hdl module version 2 requires that 2 ticks need to be subtracted from periodTicks before it is written to the DigitalIO.SAMPLE_PERIOD register on this line:

bonsai-onix1/OpenEphys.Onix1/ConfigureDigitalIO.cs

Line 120 in ce80d27

device.WriteRegister(DigitalIO.SAMPLE_PERIOD, periodTicks);

in order for the true sample rate to match the value supplied in the SampleRate property.