Connecting Front and Back End for Search Queries on Landing Page

[floriafz23]

• Implemented map_user_to_product.py in Flask app.
• Fixed all imports in product_selection files
• Added necessary installs to requirement.txt
• Implemented landing page search boxes to return values to Flask app and redirect to main page
• Implemented main page search box to return values to Flask app and redirect to main page (with new values)