The lupdate got confused of removing "Show security errors" and there being
existing string "Show style errors". lupdate thought the "Show style errors"
was a new version ("similar enough") of "Show security errors" string
instead of new string to translate. Or actually existing translated string.
So many translations got "Show style errors" translated by earlier
translation of "Show security errors".
This commit fixes the mess by manually removing "Show security errors"
references and restoring correct translations of "Show style errors" from
earlier file versions.
Good lesson to learn about lupdate behavior.
This commit adds new toolbar to the GUI for fast and easy switching of
different warning//error categories. The icons are currently just
placeholders until more descriptive icons are created.