allow plot_G_Avgs.py to parse files with variable number of iterations

[tukss]

This resizes the array on the fly to support G_Avg files with a variable number of iterations per files.

fixes #375

[hirokemono]

It still fails after reading the send file because arrays seem s to be expanded by using nsize from the first data file.

a.niter would be used to expand array size in lines 112 to 116 instead of nsize.

    gavgs = numpy.resize(gavgs, (gavgs.shape[0] + a.niter, gavgs.shape[1]))
    iters = numpy.resize(iters, iters.shape[0] + a.niter)
    time = numpy.resize(time, time.shape[0] + a.niter)

i1 = i0 + a.niter

[tukss]

The new commit actually updates niter. Thanks for finding it @hirokemono.

[hirokemono]

It works! thanks!