New Web UI

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

radicale/web/internal_data/css/icons/download.svg

@@ -0,0 +1 @@
+<?xml version="1.0" encoding="UTF-8"?><svg width="24px" height="24px" stroke-width="1.5" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg" color="#000000"><path d="M6 20h12M12 4v12m0 0l3.5-3.5M12 16l-3.5-3.5" stroke="#000000" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"></path></svg>