Fix keyboard input to master password field being blocked by shortcuts

 * Only process key events in Shortcut event handler
   if the target is the <body> element.

   If an <input> or other field has focus, it takes precedence
   over the shortcut.

 * Blur the search field when switching to an item in the details view.

   In the current UI the details view and master item list are both
   in the DOM at the same time. The details view is simply shown
   over the item list so the search field retains focus otherwise.

   This was done to allow an animated entry of the details view over
   the item list, although that has still yet to be implemented.