Make Portal make sense as the wallet landing page

[rorysaur]

Portal is currently where the user lands after creating a wallet, and in its current state it just has links to nonexistent pages which is super confusing to the new user.

1. Add links to the existing Kernel apps you can visit.
2. Indicate that all the other links have yet to be built, and disable them.
3. Bonus: Change this page's URL to not be /assets/overview since it's not actually about assets.. perhaps /home. (Or just the root / but this involves differentiating between whether the user is logged in or not, to decide whether to send them to the login page, so it might be a bit more effort at this time.)
4. Bonus: Make the app logo/title (on the left in the navbar) link to this landing page. See this example of how to specify a home URL in the navbar by using the app config.