Added loader as a common element

src/scss/components/loader.scss

@@ -0,0 +1,41 @@
+// Loader styles
+// ----------------------------------------------
+
+/* SG
+# Loader
+
+This is the generic loader for widgets, maps, components, ...
+There is only one state 'is-visible', in order to make it visible.
+
+```
+<div class="CDB-Loader is-visible"></div>
+```
+*/
+
+@import '../utilities/mixins';
+
+.CDB-Loader {
+  @include css3-prefix(animation, loader-progress 1000ms linear 1);
+  @include opacity(0);
+  @include transition(opacity, 1000ms);
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 2px;
+  background: rgba(#3AA9E3, 1);
+  z-index: 10;
+}
+.CDB-Loader.is-visible {
+  @include css3-prefix(animation, loader-progress 2000ms linear infinite);
+  @include opacity(1);
+}
+
+@include keyframes(loader-progress) {
+  0% {
+    width: 0;
+  }
+  100% {
+    width: 100%;
+  }
+}