WinForms command binding return higher affinity than XAML

There exist System.ComponentModel.Component subclasses which would be useful for binding as a command e.g. MenuItem, NotifyIcon, ToolBarButton, however others are not e.g. Timer, Process, SerialPort.

This change ensures that falling back onto hasEventTarget or defaultEventsToBind for the useful ones won't result in ReactiveUI.Platforms/Xaml/CreatesCommandBinding.cs (which returns equal affinities for these cases) attempting to handle binding instead.
Merge pull request #447 from rzhw/patch-2

WinForms command binding return higher affinity than XAML