feat(loading): add loading indicator component and styles

this is the initial commit - still needs work

references #5426

ionic/components/loading/loading.wp.scss

@@ -0,0 +1,65 @@
+@import "../../globals.core";
+@import "./loading";
+
+// Windows Loading Indicator
+// --------------------------------------------------
+
+$loading-wp-padding:                   20px !default;
+$loading-wp-max-height:                90% !default;
+$loading-wp-border-radius:             2px !default;
+$loading-wp-text-color:                #fff !default;
+$loading-wp-background:                #000 !default;
+
+$loading-wp-spinner-color:             $loading-wp-text-color !default;
+
+$loading-wp-spinner-ios-color:         $loading-wp-spinner-color !default;
+$loading-wp-spinner-bubbles-color:     $loading-wp-spinner-color !default;
+$loading-wp-spinner-circles-color:     $loading-wp-spinner-color !default;
+$loading-wp-spinner-crescent-color:    $loading-wp-spinner-color !default;
+$loading-wp-spinner-dots-color:        $loading-wp-spinner-color !default;
+
+
+.loading-wrapper {
+  padding: $loading-wp-padding;
+
+  max-height: $loading-wp-max-height;
+
+  border-radius: $loading-wp-border-radius;
+  color: $loading-wp-text-color;
+  background: $loading-wp-background;
+}
+
+
+// Windows Loading Content
+// -----------------------------------------
+
+.loading-spinner + .loading-content {
+  margin-left: 16px;
+}
+
+
+// Windows Loading Spinner fill colors
+// -----------------------------------------
+
+.loading-spinner {
+  .spinner-ios line,
+  .spinner-ios-small line {
+    stroke: $loading-wp-spinner-ios-color;
+  }
+
+  .spinner-bubbles circle {
+    fill: $loading-wp-spinner-bubbles-color;
+  }
+
+  .spinner-circles circle {
+    fill: $loading-wp-spinner-circles-color;
+  }
+
+  .spinner-crescent circle {
+    stroke: $loading-wp-spinner-crescent-color;
+  }
+
+  .spinner-dots circle {
+    fill: $loading-wp-spinner-dots-color;
+  }
+}