Fix effective stimset size extension with ITC and multiple TTL channels with different length stimsets

Only on ITC:
If multiple TTL channels are used with different size stimsets then the decimation uses the joined TTL data and decimates over the maximum stimset size. Depending on the decimation factor this leads to an extension of the shorter stimset in the data wave.

Steps to solve:

• Change logic for ITC to have single channel TTL waves, if possible use same code paths as NI.
• In DC_WriteTTLIntoDAQDataWave use a for loop over the single TTL channels of a rack and join the TTL data in ITCDataWave, use for each single TTL channel the setLength specific for that channel. From singleSetLength = DC_CalculateStimsetLength(TTLWaveSingle, device, DATA_ACQUISITION_MODE)
• revert the handling of that case in epoch creation

Start in DC_WriteTTLIntoDAQDataWave and trace the ITC path, including DC_CalculateStimsetLength and epoch creation. Check how single TTL channels are handled and how ITCDataWave is assembled. Done means each channel uses its own stimset length and shorter stimsets are not extended by decimation over the maximum length.