Simplify favorites and landing page for multi-namespace setup

[isc-tleavitt]

The common pattern in Health Connect Cloud is to have multiple dev namespaces. Our current git-source-control installation process creates a favorite link to each namespace, but really we should just create a single link and either (a) use the request context namespace, if possible, to determine namespace selection or (b) allow the user to drop in to the Git WebUI with no namespace context and support picking one right away, with a default selection of a namespace mapping to the current user's username if such a namespace exists. Really, even if (a) works, we should have support for (b) as well.

[isc-tleavitt]

Just heard some customer needs pointing back to this as well. There have also been reports/observations of favorites not being added to new namespaces, which would be ideal to investigate at the same time.

[isc-tleavitt]

@isc-akadoo, overarching goals here and for #510:

Make navigation better out-of-the-box and make it easier to add navigation post-installation after new users, namespaces are added.

• As a non-technical git-source-control user with limited IRIS-level privileges, I want to be able to add favorites to get to git-source-control pages (pull, web UI) so that I can navigate more naturally from the management portal.
• As a git-source-control user in an instance with multiple namespaces configured to use git-source-control, where I only really use two namespaces, I don't want to have tons of links to namespaces other than those two populated automatically because it's confusing if they are.
• As a git-source-control user in a instance with multiple namespaces configured to use git-source-control, where I only really use two namespaces, when I'm doing something in the git-source-control UI (Git WebUI, Pull), I want to be able to see the namespace context where I'm operating to be sure that I'm working in the right place and fix it easily if I'm not.
• (reach, optional, maybe not really feasible) As a git-source-control user in an instance with multiple namespaces configured to use git-source-control, I want links to git to automatically follow the namespace I was already in.