Activate filters and series in Streamlit UI for post-processing

[pineapple-cat]

Addresses #269.

• Filter/series addition.
• Filter/series removal.
• Redundant column type removal.

Bonus:

• YAML dump format improvement for config download. (Consistency between config yaml examples and downloaded configs from Streamlit #275)

[ilectra]

Looks pretty good! Just a couple of comments:

• Can the df not be written out into the console every time the plot is updated? If it's too hard to do this, don't worry about it.
• The update_ui function is getting a bit big. See if you can modularise it a bit/move bits of it into separate functions, and add some comments in the code of what each section does.