[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/utilities.less

@@ -0,0 +1,55 @@
+//
+// Utility classes
+// --------------------------------------------------
+
+
+// Floats
+// -------------------------
+
+.clearfix {
+  .clearfix();
+}
+.center-block {
+  .center-block();
+}
+.pull-right {
+  float: right !important;
+}
+.pull-left {
+  float: left !important;
+}
+
+
+// Toggling content
+// -------------------------
+
+// Note: Deprecated .hide in favor of .hidden or .sr-only (as appropriate) in v3.0.1
+.hide {
+  display: none !important;
+}
+.show {
+  display: block !important;
+}
+.invisible {
+  visibility: hidden;
+}
+.text-hide {
+  .text-hide();
+}
+
+
+// Hide from screenreaders and browsers
+//
+// Credit: HTML5 Boilerplate
+
+.hidden {
+  display: none !important;
+}
+
+
+// For Affix plugin
+// -------------------------
+
+.affix {
+  position: fixed;
+}