Get notified of events fired from ToolManager in Xamarin.iOS

The ToolManager'sToolManagerDelegate exposes a number of delegate methods to allow a subscriber to be notified of events that are managed by the tools framework. There are a number of methods that allow you to modify the behaviour of the tools themselves. The methods discussed here are simple notifications, so that the app may coordinate as necessary.

1. -toolManagerToolChanged:
   This method is called when the tool changes, for example changing the "active" tool in a toolbar.

2. -toolManager:annotationAdded:onPageNumber:
-toolManager:annotationModified:onPageNumber:
-toolManager:annotationRemoved:onPageNumber:
   These methods are called just after an annotation is added, modified or deleted.