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/bs.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-12 0h640v480H-12z"/>
+    </clipPath>
+  </defs>
+  <g fill-rule="evenodd" clip-path="url(#a)" transform="translate(12)">
+    <path fill="#fff" d="M968.53 480H-10.45V1.77h978.98z"/>
+    <path fill="#ffe900" d="M968.53 344.48H-10.45V143.3h978.98z"/>
+    <path fill="#08ced6" d="M968.53 480H-10.45V320.59h978.98zm0-318.69H-10.45V1.9h978.98z"/>
+    <path d="M-10.913 0c2.173 0 391.71 236.82 391.71 236.82l-392.8 242.38L-10.916 0z"/>
+  </g>
+</svg>