Replaced Bootstrap alert with Material Design snackbar

src/web/stylesheets/components/_alert.css

@@ -1,22 +0,0 @@
-/**
- * Alert styles
- *
- * @author n1474335 [n1474335@gmail.com]
- * @copyright Crown Copyright 2017
- * @license Apache-2.0
- */
-
-#alert {
-    position: fixed;
-    width: 30%;
-    margin: 30px auto;
-    top: 10px;
-    left: 0;
-    right: 0;
-    z-index: 2000;
-    display: none;
-}
-
-#alert a {
-    text-decoration: underline;
-}