Implement Sass (#568)

* Move all images to assets/img

* Move all scripts to assets/js

* Move all webfonts to assets/webfonts

* Move all files to assets/files

* Move css to assets/css and add imports

* Adjust all references to assets folder

* Fix tor icon path

* Rewrite custom css to sass and add variables

* Change ?v on style.css to 5.

* Enable Sass minification

* Remove CryptoPaper-full.7z

assets/img/flags/cu.svg

@@ -0,0 +1,13 @@
+<svg xmlns="http://www.w3.org/2000/svg" height="480" width="640" version="1">
+  <defs>
+    <clipPath id="a">
+      <path fill-opacity=".67" d="M-32 0h682.67v512H-32z"/>
+    </clipPath>
+  </defs>
+  <g fill-rule="evenodd" clip-path="url(#a)" transform="translate(30) scale(.94)">
+    <path fill="#0050f0" d="M-32 0h768v512H-32z"/>
+    <path fill="#fff" d="M-32 102.4h768v102.4H-32zm0 204.8h768v102.4H-32z"/>
+    <path d="M-32 0l440.69 255.67L-32 511.01V0z" fill="#ed0000"/>
+    <path d="M161.75 325.47l-47.447-35.432-47.214 35.78 17.56-58.144-47.13-35.904 58.306-.5 18.084-57.97 18.472 57.836 58.305.077-46.886 36.243 17.948 58.016z" fill="#fff"/>
+  </g>
+</svg>