WSUS cookbook is now windows-only!

Do not process recipes and attributes when platform is not windows.
Add legal header in attributes files.
Refactor update powershell script
Add new recipe report_viewer

Add recipe to install Microsoft Report Viewer Redistributable 2008 SP1
Add recipe server that install WSUS 3.0 SP2
Add LWRP to control WSUS server configuration

Add base_provider and base_resource in libraries for LWRP common methods.
Add new LWRP wsus_server to configure WSUS main settings.
Add new LWRP wsus_subscription to configure WSUS update subscription.
Add new LWRP wsus_notification to configure WSUS e-mail notification.
New recipe server_configuration.

Add new recipe server_configuration to configure all WSUS settings.
New recipe server_synchronize to start WSUS sync
New recipe server_freeze to create update' freeze
Fix server replica behavior