Added new SOGo configurable variable

You can change the default display when adding a shared calendar or a shared addressBook with a configurable variable inside your sogo.conf

Please note the following legend for your new configuration : 
%{FolderName} = Name of the folder; ex : Personal Address Book
%{UserName} = Name of the user; ex : John Doe
%{Email} = Email address of the user; ex : sogo1@exemple.com

See bellow for examples of how you could use the key : 

SOGoSubscriptionFolderFormat = "%{FolderName} (%{UserName} <%{Email}>)";
SOGoSubscriptionFolderFormat = "%{UserName} : (%{FolderName})";