[FEATURE] - Support (favorite) projects to be stored in User Settings

[alefragnani]

Today, the (favorite) projects are stored in a file called projects.json. It is stored in VS Code internals, and you have the possibility to use a different location via projectManager.projectsLocation setting, if you need, for instance, share the projects with other VS Code release or even to sync using any sync service.

The idea of this issue is to allow the user to store their projects in User Settings, as an alternative to the projects.json file concept. It's not meant to_combine_ projects.

Issue #525 asks for projects to be stored in GitHub Gist, in order to allow sync, since Settings Sync won't allow external files to be synced. Issue #712 asks for multiple values to projectsLocation, (which raises a few concern, like how to know in which of the projects.json file a new project should be saved). So, storing the projects in the User Settings would solve, at least, the settings sync support.