Caliburn.Light 3.1.0

• change Validation to be reflection free
• don't create new strings in validators (pre-format error messages)
• remove usage of Expression<Func<TProperty>> to extract the property name
• initial documentation update
• add BindableCommand as base class of DelegateCommand
• remove support for static subscribers in EventAggregator
• optimize EventAggregator for async subscribers
• UAP: support cal:Bind.CommandParameter with x:Bind
• UAP: support special value in DelegateCommand.OnEvent
• UAP: enable nameof() usage with NavigateHelper