colors for visual grouping of customer, projects and activities (#751)

assets/sass/print.scss

@@ -0,0 +1,10 @@
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+@media print{
+    .sf-toolbar, .control-sidebar {display: none !important;}
+}