Redo navbars one more time

Forgot to open this earlier, but doing so now to track.

With the revamp of the navs with flexbox, I need to revisit the navbar. It was originally built to utilize the .nav base class and relied on those .navs stacking on narrow viewports. Now that navs are inline to start, we need to redo some of this.

Luckily, I had bit of this in mind while redoing the .navs in flexbox. Here's what we need to change:

• Redo the navbar flex styles to be columned by default, allowing us to have fewer overrides.

• Rebuild the .navbar-nav to no longer require .nav. There's not enough value there and we need to override padding and alignment too much.

• Drop the flex-grow: 10 from .navbar-nav and utilize the auto margin utilities.

There are a few other tweaks to be made, but those are the major ones.