Add timeline menu toggle to nav panel

This is to address problems people have with the current timeline navigation being restricted to timeline header without giving up compactness.

Timelines in side nav panel now expands to a list of timelines, it stays open until you close it yourself so people can keep it always open if they want, or if they don't switch often they can keep it closed.

I also renamed "Timeline" to "Home Timeline" to try clear up some confusing naming. maybe it should be called just "Home" though?

I also don't know yet if we should keep the chevron to indicate something that can be opened for the Timelines button.