Add "Export selection to" menu item in Log Dialog

By @ch3cooli on November 10, 2012 12:29 (imported from Google Code)

"Export selection to" exports selected files to a folder recursively.
This is a useful function to export changed files recursively.
Currently, It is only available in Changed Files Dialog.
It is better to also have this function in other dialogs, such as Log Dialog, Commit Dialog.

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