Task 1 - Update the navigation bar look and feel and links

[lpalbou]

Task requirement from Noctua Landing Page Project

The navigation bar should have the same design as the one used on geneontology.org. Links to HTML pages and SASS from GO site:

• https://github.com/geneontology/geneontology.github.io/blob/master/_includes/topnav.html
• https://github.com/geneontology/geneontology.github.io/tree/master/_sass/custom

The GO logo should also be clickable and redirect to the main geneontology.org site.

The navigation bar should also contain two links:

• About Noctua
• Curation Manual

As well as a dropdown icon on the right for login/account preferences

Linked to #2