Allow launch settings to be created at the user level

#### Repro
1. Create a .NET Core console app
1. Go to project settings, Debug property page and fill in _Application arguments_.
1. F5 to debug the app launched with the specified arguments

#### Current behavior

The project system creates ```launchSettings.json``` file. If the project is under source control (e.g. git) the user needs to add it to ```.gitignore``` file or it ends up in the repo, where it affects everyone who works on that project even though the settings are in many cases meant to be used just for a few debugging sessions on the dev machine.

#### Proposal

Introduce a predefined profile `````` created by default for a new project. This profile would be persisted in ```.suo``` file instead of ```launchSettings.json```. If the user wants to define settings to be used by other contributors to the repository they do so by creating a new profile.

If the ```.suo``` file doesn't contain any settings for given project and ```launchSettings.json``` is present, the settings in the first profile in ```launchSettings.json``` would be used to initialize the _user specific_ profile. That way the repository can contain defaults for the developers working in the repo.