Staff page, navbar, image filesystem overhaul

- Add a "meet the team" page with the names and bios of staff members
- Add a navbar to the top of every page
- Move and rename header images to a more consistent system

New files:
- managers.html - A page for our bios
- watson-100/200/1000.jpg - My picture, in various sizes
- donors.png - The header image for the donors page (not new, just
moved)
- index.jpg - The header image for the homepage
- managers.jpg - The header image for the staff page
- placeholder-100/200/1000.jpg - A simple placeholder image for bios
with no photo

Removed files:
- globe.jpg - Cropped, resized, and moved to headers/index.jpg
- placeholder-person.png - Moved to headers/donors.png