Incorporated pull requests #1305 and #1306.
Restored declaration of 'hidden' class to index file.
Restored h2 in sections for navigation purposes.
Cleaned up index.html.
Updated web UI to a more modern interface while keeping the HTML structure as similar to the original as possible.
New features include:
-Mobile view compatibility
-New light color scheme using primary colors based off Radicale's official colors
-Dialog theme for most sections
-Floating Action Buttons (FAB's) for creating and uploading a new collection
-Commands to edit/delete a collection have become buttons that only show on hover.
-Improved loading screen
-New loading circle with consistent color scheme
-More explanation for dialog text
-Added warning to delete screen
