Heavy load on ITC causes stimulus update delays

A heavy load on the ITC can degrade experiment performance and lead to delays in updating the stimulus display.

If the volume of data from the ITC is high, the performance degradation probably results from a large number of variable notifications. We could potentially fix this by batching the data in an array and including it in a single announcement, instead of announcing each value individually.

If the experiment uses many ITC channels, the performance degradation probably results from too many threads contending for CPU time. We should investigate better ways to handle such a load.