Add a new "lang" attribute and variable
Add jquery validation to javascript minify
Add jquery validation translation files and properly load them in html
Add javascript to run validation on any form[data-validation]

To simplify the login/logout, assemble all the handling of form
authentication into a single cherry tool. 
This new tools support the following feature:
- handle the session
- validate credential
- show login form when not login
- redirect to original page
- setup the `cherrypy.serving.request.login` with user object

Not every plugin does provide a templates or locales directory. So we
need to make it conditional.

Make testcases run in py2 and py3

translation too.

resquest/response.

accept-language.

accepted language.