Replace launchSettings.json with MSBuild properties

In legacy projects, debugging settings were specified in the project file:

```xml

Program
C:\MyRemote\Executable.exe
true
MyRemoteMachine

```

With SDK-style projects, they're kept in `launchSettings.json` which is a hold-over from the `project.json`/`.xproj` days:

```json
{
"profiles": {
"ConsoleApp152": {
"commandName": "Project",
"remoteDebugEnabled": true,
"remoteDebugMachine": "MyServer"
}
}
}
```

This file is stored in the `Properties` folder and tends to end up in version control.

Now that we support remote debugging, putting the remote host name in version control does not make much sense. We want to put _some_ of these values in version control, and others in the user's local state.

By moving the properties to the project we could have some in `.csproj` and others in `.csproj.user`. Longer term we could control them per configuration/target framework/other dimension.