de/de-informal language updates / fixed using mailprefix in registration and password lost notifications

fixed resizing mediamanager panels in Chrome using browser sniffing (FS#2351) - any better solution welcome

Changes to plugins cascade for FS#2359

renamed plugins.protected.php to plugins.required.php and added it cascade to allow overwriting as a local protected file

pt: paraphrased '<' character in some language files to avoid XML errors

as per commit 34bc7405

paraphrased '<' character in some language files (en, de, de-informal) to avoid XML errors -- please fix other languages

re-added font-size to .ui-widget of jqueryui theme to make programmatical removing of font-family easier

fix widths of panels in fullscreen mediamanager to be 100% when resizing (FS#2351) -- please test in different screen sizes, etc

This fixes password changing operations: password change and user
modification are two different operations on the AD backend - the user
modification should not be done on password only changes.