Enhancement: add site logo and favicon

[ngjunsiang]

I have just uploaded favicon.ico and assets/icon-circle.png. These should be incorporated into the page, using favicon.ico in the tab title and placing the icon beside the site title

Task

1. Make any necessary changes to have the favicon show up
2. Make appropriate changes in the base template html and css to have the icon show up

Deliverables

• add favicon.ico (in content branch)
• add icon files in /assets (in content branch)
• Favicon appears in tab title
• Logo appears on all pages, beside page title