Website redesign: unify hub pages and polish contribute/webapps layouts - #277

Changed pages include:

• index.html - view
• 404/index.html - view
• affiliated-apps/index.html - view
• archived-apps/index.html - view
• calendar/index.html - view
• code-of-conduct/index.html - view
• contact/index.html - view
• contribute/index.html - view
• contributors/index.html - view
• core_developers/index.html - view

There are more changes not included in the list