Account management new

[Carla-Moz]

This is a hefty PR and I apologize in advance. I promise future PRs won't be so large.

Major changes include the following:

1. Centered container for all pages
2. Navbar and footer with routes to pages and external links
3. Sign-out functionality in drop-down of navbar
4. New account management styles which will probably change so let's keep as placeholder for now
5. Added Sass to the platform; there are still some lingering in line styles that need cleaning up as the sass files evolve. Might also be some repeating styles which I'll clean in next PR.
6. Not responsive yet; that's for the next PR.

[rhelmer]

lgtm overall, I didn't focus on the style changes too much (except verifying that it looks and works ok visually), just a few minor things I noticed.