write a info message to the log if a file gets removed from the trash bin automatically

From time to time we get complains that a file doesn't end up in the trash bin. Often this happens because the file is to large for the users quota (the trash bin doesn't use more than 50% of the currently available free space). In this case the expire() function removes the file from the trash bin again.

To make this more transparent for the user this patch writes a Info to the log file every time a file gets expired. Additionally it adds a short explanation of the expire function to the app description of the deleted files app and the versioning app.