Multi root support: warn developer when asking for a setting for a resource but the setting is not resource scoped

[egamma]

When in Dev mode

• Accessing a resource configuration with out providing a resource will log following warning

[ms-vscode.configuration-sample] Accessing a resource scoped configuration without providing a resource is not expected. 
To get the effective value for 'conf.resource.insertEmptyLastLine', provide the resource for which the value is needed. 
If you would like to look up all values, use 'inspect' method instead.

• Accessing a window configuration for a resource will log following warning

[ms-vscode.configuration-sample] Accessing a window scoped configuration for a resource is not expected. 
To associate 'conf.view.showOnWindowOpen' to a resource, define its scope to 'resource' in configuration contributions in 'package.json'. 

Following message is shown when a window setting is configured in Folder settings