Office 365: Bulk add users/groups to Lync 2013, all at once [SOLVED]

Here you find a powershell script which was very useful for me.
All scripts are free of charge, use them at your own risk :

This week I’ve migrated a client to Office365.

They wanted to add all users to their Lync client at once.

This is not a standard feature of Lync.

The only way to work around this problem is, creating a Security group, and add the security group to Lync.

Create a new security group and Add all of the Lync users to this group.

In Lync, add the name of the group.

When finding the group, click right and select ‘Add this list to contacts’.