Revamp Projects/Research pages

[QuillPusher]

• Created writeup for a static Research Page

• Removed Menu items under Research and added them as sub-projects on Projects page

• Added unique writeups for project summaries in projects.yml

• removed menu items from under projects menu

• created a projects.md page, to pull project excerpts from projects.yml

• linked existing detailed project pages (e.g., vetorautodiff) within projects.yml, to ultimately show on the projects page

• projects.md: looped through projects to filter them based on the respective Research Area (category attribute in projects.yml) and displayed relevant projects under respective Research Area heading in project.md page

• added a step-by-step tutorial in readme for future site contributors to be able to add more projects to the website (this tutorial section will grow as the site revamp continues)

• Unused code (drop-downs for Research and Projects menu items) is now commented in the header file

• Images of resultant pages are attached for reference:

• Research (static page)

• Projects (dynamically generated)

[QuillPusher]

Closing this PR since it doesn't fit the latest requirements. Will add a new one with the latest changes.