running average and standard deviation of vectors

[running_avg, running_std] = running_mean_std( data, filter_width )
returns the running mean and standard deviations of either a vecotor or matrix.

for the case of data = vector of length N, it will return a running average and
standard deviation for a window of width filter_width. The output vectors have length N; however,
to avoid edge effects NAN's are placed in the front and end: running_avg(
[1:N, end+1-N:end]) = NAN.

for the case of data = vector of 2XN or NX2, it will return a running average and
standard deviations for the first row (column) and the second row (colum) for a window of width filter_width.
The output vectors have length N; however, to avoid edge effects NAN's are placed in the front and end: running_avg([1:N, end+1-N:end]) = NAN.

for the case of data = matrix MXN (i.e. a b/w picture), it will return a running average and
standard deviations for a filter, which is a filled circle with diameter filter_width.