[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/close.less

@@ -0,0 +1,34 @@
+//
+// Close icons
+// --------------------------------------------------
+
+
+.close {
+  float: right;
+  font-size: (@font-size-base * 1.5);
+  font-weight: @close-font-weight;
+  line-height: 1;
+  color: @close-color;
+  text-shadow: @close-text-shadow;
+  .opacity(.2);
+
+  &:hover,
+  &:focus {
+    color: @close-color;
+    text-decoration: none;
+    cursor: pointer;
+    .opacity(.5);
+  }
+
+  // Additional properties for button version
+  // iOS requires the button element instead of an anchor tag.
+  // If you want the anchor version, it requires `href="#"`.
+  // See https://developer.mozilla.org/en-US/docs/Web/Events/click#Safari_Mobile
+  button& {
+    padding: 0;
+    cursor: pointer;
+    background: transparent;
+    border: 0;
+    -webkit-appearance: none;
+  }
+}