Allow network managers to use the new network catalog as their network home/front page

[SteelWagstaff]

As a network manager, I may want to replace my network home page with my new network catalog. I cannot currently do this easily myself, since Aldine doesn't provide a GUI interface to change the network front page and Aldine has some hardcoded display rules for the 'front page'.

The only way a network manager could do it now is by manually changing the 'page on front' setting for the theme in site-settings:

If they do this, the front page/catalog CSS conflicts and the page appears broken:

We will likely need to modify the front page template/CSS, the customizer (to let them chose their network front page), and possibly some of the other page templates/theme settings.

[SteelWagstaff]

Tested and works as expected on integrations.