Documentation panel should be pinned to bottom of page

[sersorrel]

It would be really nice if the documentation panel:

didn't jump around as you change pages within the application; when there's space, it should sit at the bottom of the page, not flush against the main application UI (but when there isn't space, it should overflow off the bottom of the screen like normal).

This is probably possible with flexbox – put a flex-grow: 1 on the #root, put the #root and the doc panel in a display: flex div together, set the div to be justify-content: space-between and you're probably most of the way there.

The fixed bottom navbar is a slight snag; either add a fixed amount of margin below the doc panel (the current 90px seems to be enough for when the bottom navbar content overflows onto two lines), or add a visibility: hidden copy of the navbar inline (not .navbar-fixed-bottom) at the end of the page.