Updated OPV_wx_GUI.py

[lenasush]

1. Added a zoom-in button under each plot.
2. This button opens a window with a Plotly styled plot with all the features of Plotly, like zoom in and out, see actual data values, save a plot as an image, etc.
3. In the average calculation part I found a bug and fixed. But still, need to work on improving the format of the output file.