webglapp: when resampling, the default minNeighbors is now 2 instead of 0.

This means that when the adjacent node is too far (Gaussian weight below 1%)
then at least the next node will be looked at to see if its weight is over 1%.
This helps skip nearby nodes when there are locally distorting artifacts
such as cracks or folds, while still using nodes in the second-adjacent
section (given a sufficiently large sigma, and assuming a serial section
registration approach that considers some sections beyond the immediately
adjacent ones).