Update users' locales when their language is made invisible

[mconf-daileon]

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Author Name: Leonardo Daronco (Leonardo Daronco) Original Redmine Issue: 1476, http://dev.mconf.org/redmine/issues/1476

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Consider the scenario:

• There are two languages visible in the site: "en" and "pt-br"
• A user sets his language to "en"
• An admin hides the "en", leaving only "pt-br" visible
• The user that had his language as "en" will still have his language set to "en" (and the site will still work in "en")

There could be an option for admins to "clear users' locales", that would get all users that have a locale that is not visible and change their locale to the default locale.

This could be done automatically when a locale that was visible is made invisible, but that might not be good for cases when a locale is hidden temporarily or by mistake. A new option/button (with a confirmation dialog) that just sets users' locales might better.