Import panel:

- added pskl.controller.settings.ImportController (empty atm)
- moved SettingsController under settings namespace
- move settings templates in a dedicated folder
- created import icon (svg is in the resources folder)
- added import button in right-layer

templates/settings.html

@@ -25,6 +25,13 @@
     <span class="label">GIF</span>
   </div>
 
+  <div
+    data-setting="import"
+    class="tool-icon import-icon"
+    title="Import an existing picture"
+    rel="tooltip" data-placement="left">
+  </div>
+
   <div
     class="tool-icon upload-cloud-icon"
     title="Upload as a spritesheet PNG"