[Forward port to master] - Give proper heading name to "Edit configuration" column

Steps:

1. Login to cms
2. Go to channel perspective and enter into a channel.
3. Click on the edit button to create preview configuration ,so that "Edit configuration" is displayed under List of channels.
4. Go to Channels List .
5. Notice Edit configuration is shown in front of the channel.But no column heading is shown.
6. Also for a user, it's confusing if he doesn't want to see "Edit configuration" column and chooses to remove it from columns then blank heading is shown while selecting it.

Check screenshot for reference.