[Enhancement]: Update sidebar css + settings

[sirmspencer]

What do you suggest?

A couple things could be better about the side bar history panel.

1. Move the header outside the scroll area so it stays visible.
   
   
   That will match the bottom panel
   

2. When unchecking the history box, hide the now empty div
   

3. Add default history height as a setting. It always starts quite squished.