Adding Plotly's interactive features to BeamAnalysis

[waynemaranga]

Proposing to add more interactive features in notebooks using Plotly, the first one being BeamAnalysis.plot_interactive_results() that plots a simple interactive plot using Plotly with minimal difference from the plot_results() using Pyplot. The key differences have been commented in, but the basic functionality is the same: it plots a Figure.

This change introduces a new dependency: plotly

Future interactive features based on this:

1. Using Click Events in Jupyter https://plotly.com/python/click-events/#update-points-using-a-click-callback
2. Animating Influence Lines https://plotly.com/python/animations/#animated-figures-in-dash
3. A fully fledged frontend using Dash