Handle groups with spaces

Migrated from: https://tracker.clearos.com/view.php?id=933

Reported by: Peter Baldwin

Though the GUI does not allow adding groups with spaces, there should be a way for the mail extension to handle setting the distribution list e-mail address for such groups. For example, a group name of "test group" needs to use something like "test_group@example.com" for the group distribution list. It's tricky since "test_group" might already exist. Perhaps there is a valid character for e-mail addresses, but not permitted for group names?

http://en.wikipedia.org/wiki/Email_address#Valid_email_addresses

Bug comment 1:
This affects samba shares as well especially with flexshares where the default group of "domain users" is applied to a flexshare under active directory. To fix this in a flexshare, double-quotes can be added to the group name for example, the default behavior renders the valid users as:
valid users = @"%D\domain users", @domain users

When it should be:
valid users = @"%D\domain users", @"domain users"

Added tracker 0002261 for Flexshare (Samba) issue.