Provide basic plot styling options for flexplot

[FoxxMD]

I love the customization available for flexplot but the hardcoded styling for plot() falls short when visualizing a single metric over a short time period.

Here I look at cpu % over a 30 second period, with y-axis set to 0-100:

At a glance it's not super clear what the trend looks like.

Changing this line back to linestyle='solid' makes the graph much more readable at a glance.

Please provide styling options in the command so this would be possible, thanks!