Update tag list template to allow renaming.

Update tag list template to allow renaming.

* Add a form on each tag to handle rename action.
* Add JavaScript to handle action on the corresponding page inside the global index.js file.
* Add support for the 2 active themes : material / baggy

The form solution is cleaner than an Ajax one because it let the browser validate input data and make the POST easier without the need to handle JSON response.