Added quota information (max-quota and used-quota) to the listuser output.

For regular output the columns qmax and qused were added:
Id Name Displayname Email qmax qused
2 mailadmin The Admin admin@devel-mail.netline.de 0
3 andreas John Doe andreas@devel-mail.netline.de 0

Also, the CSV output contains now the values for MaxQuota and UsedQuota