Add initial expanded projects list with links to overview pages

[dannon]

xref #1428

Looks like this:

@wm75 Feel free to take this over and run with it if you want

[wm75]

Thanks @dannon - that's exactly what I had in mind!
@beatrizserrano @bebatut I will try to work on the "Core Team Projects" landing page above. Maybe you could start thinking about what a corresponding "Community Projects" landing page could look like? Maybe we really want to put the current not-so-visible "Communities of Practice" section there? In principle, we could list any community in the new dropdown menu that has somebody willing to create a hub page for them?

[beatrizserrano]

I think that the "Communities of Practice" deserve a more prominent place, but I don't see them as projects. My understanding is that those communities meet regularly because they share an interest, not because they work on the same project. We could have a separate page for the communities of practice and another for the communities by location and add them under the "Community" menu instead of "Projects". And we could expand that information for those communities as much as the communities like, e.g. adding the different projects in which the members are involved.