Bug 691647 Part 1: clean up nsISidebar interface by removing the non-standard addPersistentPanel/addPanel methods, and adjusting method arguments to avoid the use of string/wstring. r=jst, sr=sicking

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extra : rebase_source : f8214c757d49f433c37563e9ceed86e81f25eb1e
Bug 691647 Part 2: remove Firefox Desktop implementation of removed nsISidebar methods. r=dolske

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extra : rebase_source : 7981dd516a4098d7ebc85b9c406163d30d4ebac3