Restore inner scrolling of data table and profile input

[nrenner]

This is already an item in #66:

Data table does not scroll (sidebar container does), thus table header disappears

But as I wanted to explain better in advance, here some more notes.

@poutnikl also commented on this in #80:

[...] having the horizontal slide bar below the whole segment data is somewhat inconvenient.

The current implementation of profile and segment data together in the sidebar and the previous with segment data only both rely on the sidebar component to do the scrolling.

I think this is not an adequate alternative to the old implementation (current brouter.de/brouter-web), where the profile textarea and the data table component did the scrolling. Because with sidebar scrolling, the footer (profile buttons and horizontal table scroll) disappear and it's very inconvenient to first need to scroll there. Or new users might not even notice that there are profile buttons. Also when scrolling down, the table header disappears, which makes it harder to look up a specific column, especially when the contents look similar. But I'm open for other arguments.

Let me know if I can point you to how it used to be (using flexbox). You might also encounter that DataTable issue.