Added JS for dealing with setting the custom theme

app/static/js/customThemes.js

@@ -0,0 +1,11 @@
+function changeTheme() {
+    // Get the selected theme for the dropdown
+    var themes_select = document.getElementById("themes_select");
+    var selected_theme = themes_select.options[themes_select.selectedIndex].text;
+
+    // Update the theme cookie
+    document.cookie = "theme=" + escape(selected_theme) + "; Path=/;"
+    
+    // Finally reload the page to let the new theme take effect
+    location.reload();
+}

app/templates/layout.html

@@ -32,6 +32,7 @@ Haldis - {{ active_page|capitalize }}
     {{ super() }}
     <script type="text/javascript" src="{{ url_for('static', filename='js/theme.js') }}"></script>
     <script type="text/javascript" src="{{ url_for('static', filename='js/timer.js') }}"></script>
+    <script type="text/javascript" src="{{ url_for('static', filename='js/customThemes.js') }}"></script>
 {% endblock %}
 
 {% block navbar %}