localize jQuery UI date picker FS#2912

Fix issues from teams:i18n:translation-check in localizations

removed unused lang string (authmodfailed)

Language files: insignificant fixes

fixed language file placeholders FS#2682

removed outdated language string. it has to be retranslated

localization: removed strings from old flashuploader

Remove references to (un)?subscribens.

removed remnants of old flash uploader (FS#2335)

jqueryized locktimer

removed duplicate authors from language files

added 'register' and 'resendpwd' to action links and buttons

Attention: $lang['register'] has been renamed to $lang['btn_register'],
anyone using that in any plugin or template should adjust it.