[IMP] all: new design to match the one on odoo.com

* upgrade to bootstrap 3.3.6

* new Header, port website LESS
  - Add the new header
  - Modify sub-header in order to handle “back” button and version
    switcher
  - Port website’s Less:
    * Use same variables’ names
    * Review fonts and colours in order to fit the new style

* add new footer

* Review and optimise JS code in order properly handle the new header,
  footer and card.top animations

* replace  banner images

_extensions/odoo/static/bootstrap-3.3.6/less/responsive-embed.less

@@ -0,0 +1,35 @@
+// Embeds responsive
+//
+// Credit: Nicolas Gallagher and SUIT CSS.
+
+.embed-responsive {
+  position: relative;
+  display: block;
+  height: 0;
+  padding: 0;
+  overflow: hidden;
+
+  .embed-responsive-item,
+  iframe,
+  embed,
+  object,
+  video {
+    position: absolute;
+    top: 0;
+    left: 0;
+    bottom: 0;
+    height: 100%;
+    width: 100%;
+    border: 0;
+  }
+}
+
+// Modifier class for 16:9 aspect ratio
+.embed-responsive-16by9 {
+  padding-bottom: 56.25%;
+}
+
+// Modifier class for 4:3 aspect ratio
+.embed-responsive-4by3 {
+  padding-bottom: 75%;
+}