Related to CORE-4539

When purchasing a hosting plan with free domain, the domain is activated and is assigned a parent of the hosting plan. This is good because it means that the hosting plan can't be cancelled independently of the domain to get a free domain forever.

The downside is that the domain doesn't appear in our list of domains. It's not shown in the domains widget on a client profile page, or under Billing > Domains, or on the client's dashboard in the client area. This presents a problem, as we should be able to see all our active domains in one place in all 3 of these places.

I would suggest that we show all domains, whether they are parent or children within the domains widgets. However, if they have a parent, we should flag them some way so that we know they are linked to another package/hosting account.

Under Billing > Domains, add another option called "Parent" next to Manage, if the domain has a parent. It should link to the management of the parent. This should be sufficient here.

Under the Client's Profile page, do the same thing, add an option "Parent" next to Manage, if the domain has a parent. It should link to the management of the parent.

In the client area, in the domains widget, I'm not sure yet what we should do. Any suggestions? Perhaps we add the following in the expand area if the domain has a parent:

"This domain belongs to [package name] - [package label]. If that service is cancelled, this domain will be cancelled as well."

Make "[package name] - [package label]" link to the management page of this parent service.