Enhance IIS cookbook to include some missing configuration options

The current LWRP for IIS are missing several options for configuring IIS. A few new options have been added.

### pool.rb
 * [startMode] - AlwaysRunning, OnDemand
 * [autoStart] - True, False

### app.rb
 * [preloadEnabled] - True, False

Ticket https://tickets.opscode.com/browse/COOK-4709