Add texture/styling distinctions for line plots

[jsoules]

As part of looking at color tests, I've realized that we just have too many potential data series for color alone to be sufficiently distinctive for all viewers. It would be helpful to include a corresponding variation in line styling (dots, dot-dash, etc.) to help differentiate data series.

[magland]

I think the user is not as interested in knowing which plot series correspond to which chain IDs, but rather in seeing the distribution of plot series, to see if they are converging to roughly the same distribution. Also, I think we should focus on the case where the number of chains is just 4 to 8.

[jsoules]

see also https://stackoverflow.com/questions/53327572/how-do-i-highlight-an-entire-trace-upon-hover-in-plotly-for-python