Install GitHub App

[svenefftinge]

Allow installing the GitHub app from the gitpod.io dashboard.
The user should be able to install it on their own user or any of their orgs.

This is the first step of the project creation flow and shall be reachable through https://gitpod.io/new.

User Experience goal

The user should be able configure Prebuilds for a project by either installing the GitHub app for GitHub or installing a webhook for GitLab and Bitbucket.

Proposal

In this first MVC (minimum viable change), we can do the following:

1. Introduce a full page for setting up a new project.
2. An option to reauthorize which will reconfigure the GitHub app or update the webhook.
3. An option to change the provider from the ones already connected.
4. An option to associate a team for a project.
5. An option to create a team during project import.
6. A new projects list for the team surfacing project name, git repository, active branches, and the latest prebuild status.

Designs

Aurthorize	Projects List	Select Account

Select Team	Create New Team

Team Projects	Team Projects (Hover)

See also design specs.