Replaces non ascii characters to dashes so that it's consistent with … (#260)

refs #7313

- theme name normalisation
- detect duplicates to show a popup to override a theme

app/components/modals/upload-theme.js

@@ -47,7 +47,8 @@ export default ModalComponent.extend({
 
     actions: {
         validateTheme(file) {
-            let themeName = file.name.replace(/\.zip$/, '');
+            let themeName = file.name.replace(/\.zip$/, '').replace(/[^\w@.]/gi, '-');
+
             let availableThemeNames = this.get('availableThemeNames');
 
             this.set('file', file);