Enhance report plots

[adelavega]

Closes #679
Turns out that making SVGs and PNGs with Altair is a pain, because we need to install Firefox or Chrome + Selenium. This is doable, but would require re-doing the way our Dockerfile is set up, as installing these has failed so far.

Instead, I made some updates to the aesthetic, making it easier to interact. I think by removing the "interactive" from the top part, and making the legend easier to click on, the plots are more responsive.

I think to deal w/ performance issues in #533 we can either close unused components (and even re-fetch the report), or only allow a single report to be shown at once.

Even then, for very large designs this may be an issue but we can deal with that when it happens.