Add popout window functionality for dashboards

[Sujay-Shankar]

@DanielAndreasen brought up a good point that gollum should support the creation of windowed dashboards instead of only relying on jupyter's functionality. We decided to sort of pop this out of the JOSS paper review process and treat it as a standalone issue for a future version release.

Basically, we'd want to make better use of bokeh's inner workings with the bokeh serve --show script.py behavior, probably, or maybe something more advanced and less scripty, if we find that in the future.