Implement theme admin UI to support previewing

LEARNER-2017

cms/static/sass/bootstrap/studio-main.scss

@@ -3,7 +3,7 @@
 // -----------------------------
 
 // Bootstrap theme
-@import 'bootstrap/theme';
+@import 'cms/bootstrap/theme';
 @import 'bootstrap/scss/bootstrap';
 
 // Variables

cms/static/sass/elements/_system-feedback.scss

@@ -72,6 +72,60 @@
   }
 }
 
+.page-banner {
+    max-width: $fg-max-width;
+    margin: 0 auto;
+
+    .user-messages {
+        padding-top: $baseline;
+
+        // Hack: force override the global important rule
+        // that courseware links don't have an underline.
+        a:hover {
+            color: $link-color;
+            text-decoration: underline !important;
+        }
+    }
+
+    .alert {
+        margin-bottom: $baseline !important;
+        padding: $baseline;
+        border: 1px solid;
+
+        .icon-alert {
+            margin-right: $baseline / 4;
+        }
+
+        &.alert-info {
+            color: $state-info-text;
+            background-color: $state-info-bg;
+            border-color: $state-info-border;
+            box-shadow: none;
+        }
+
+        &.alert-success {
+            color: $state-success-text;
+            background-color: $state-success-bg;
+            border-color: $state-success-border;
+            box-shadow: none;
+        }
+
+        &.alert-warning {
+            color: $state-warning-text;
+            background-color: $state-warning-bg;
+            border-color: $state-warning-border;
+            box-shadow: none;
+        }
+
+        &.alert-danger {
+            color: $state-danger-text;
+            background-color: $state-danger-bg;
+            border-color: $state-danger-border;
+            box-shadow: none;
+        }
+    }
+}
+
 .alert, .notification, .prompt {
 
   // types - confirm

cms/static/sass/partials/cms/base/_variables.scss

@@ -241,6 +241,7 @@ $ui-action-primary-color-focus: $blue-s1 !default;
 
 $ui-link-color: $blue-u2 !default;
 $ui-link-color-focus: $blue-s1 !default;
+$link-color: $ui-link-color;
 
 // +Specific UI
 // ====================
@@ -281,3 +282,23 @@ $action-primary-active-bg: #1AA1DE !default; // $m-blue
 $very-light-text: $white !default;
 
 $color-background-alternate: rgb(242, 248, 251) !default;
+
+// ----------------------------
+// #COLORS- Bootstrap-style
+// ----------------------------
+
+$state-success-text: $black !default;
+$state-success-bg: #dff0d8 !default;
+$state-success-border: darken($state-success-bg, 5%) !default;
+
+$state-info-text: $black !default;
+$state-info-bg: #d9edf7 !default;
+$state-info-border: darken($state-info-bg, 7%) !default;
+
+$state-warning-text: $black !default;
+$state-warning-bg: #fcf8e3 !default;
+$state-warning-border: darken($state-warning-bg, 5%) !default;
+
+$state-danger-text: $black !default;
+$state-danger-bg: #f2dede !default;
+$state-danger-border: darken($state-danger-bg, 5%) !default;