Implement 'extract_plane', `extract_section` feature to WData.py
extract_plane:
This feature would extract a plane when dim=3 and create a helper WData structure that one can plot using matplotlib. This plot would be a colorbar plot
exteract_section: (I do not completely like this semantics, as it can implies that one can get a section of data)
This feature would extract a cross section when dim=3,2 and create a helper WData sctructure that one can plot using matplotlib. Whis plot would be a line/scatter plot.