Add some project import onboarding for first project/builds

This adds some messaging for the first project import, but only for the first 5 builds. This also adds a demo project import, which is currently our template project, which is imported with one click. Some guidance is added for the following scenarios on the project detail page:

* Project has no builds (should never be the case, but added anyways)
* Project is building, please wait
* Project has a failing build, link to FAQ for now
* Project has a passing build, set up a webhook

In the future, this should track user input, so onboarding can be closed -- though it isn't intrusive messaging right now either.

On the dashboard page, onboard messaging prompts the user to import a new project, or import the demo project. Clicking this button will attempt to import the project for the current user. The project is be named "<username>-demo", this could be randomized in the future. Possibly outcomes are:

* Template project not imported yet, import project
* Template project already imported by user, redirect to project page
* Template project imported by user and renamed, redirect to project page (detection is done by repo url)
* Project named for collision by another user -- this should maybe back down to a randomized name? This is not implemented, it will simply throw an error