XWIKI-13786-2: Accessibility problem with rights management's checkboxes states (#2051)

* XWIKI-13786: Accessibility problem with rights management's checkboxes states
* Added tabindex for the checkboxes (access through keyboard).
* Added keyboard responsiveness to the checkboxes.
* Fixed a loss of focus when changing the state of a right by validating it.
* Tested changes manually with a screen reader (orca-debian)
* Added comments
* Added some L10N support
* Wrapped the image in a button, and moved behaviur to this button.
* Added a 'nextstate' function for code factorization.
* Fixed the event listener instantiation to a more up-to-date way.
* Fixed the event listener instantiation to reduce Prototype usage.
* Removed the (unused) label from the rights-edit. See https://github.com/xwiki/xwiki-platform/pull/2051#discussion_r1086354379