Support for the Enabled property of Components in the WinForms command binder

While trying to bind a command to a System.Windows.Forms.ToolStripButton, I noticed that its enabled state was not updated correctly with changes to the command's CanExecute. Upon further investigation, this was caused by the fact that ToolStripButton is *not* a Control, but derives from Component instead. Apparently, there are Components that are a lot like Controls and should therefor support command binding like Controls do. ReactiveUI only updates the Enabled property for classes deriving from Control though.

I've added the test "CommandBinderAffectsEnabledStateForComponents" to illustrate this problem. The changes to CreatesWinformsCommandBinding make the test pass.

I've replaced the check for targetType being a Control with a check for targetType being a Component (Control derives from Component). Alternatively, we could also scrap this check altogether and only do the check for an Enabled property on targetType.