Allow independent scrolling of sidebar, filter and main content sections

[abhishek-compro]

Currently, scrolling the page also scrolls the sidebar as well which is bit annoying when there are lot of tables and links.

I was able to fix this by setting height: 93vh in both div.sidebar_wrapper, div.left_column and div.right_column. This is good enough for me. Let me know if I can open a PR for this.

[dantownsend]

Yes, I can see this being useful. Using 93vh as the height might be a bit brittle, as does that assume the top nav is a certain height? If you want to create a PR, I'll pull it down and take a look.