Added a new link annotation functionality to the core API's and build up a RI implementation. Basic support for create link annotation using the link annotation tool is supported as well as using the delete key to removed annotations.

When an annotation is created various collection are updated to get the annotation on the screen but more importantly the state manager is updated with all the objects need to be changed due to the new annotations.

Support for undo is not currently setup but will likely come pack to this at a later date.

It is now possible to use the toolbar tool 'Link Annotation Tool" to create page level annotations. When the tool is selected the user can draw a rectangle on a page using a click an drag mouse movement. When the mouse is released then a new annotation will be drawn. The toobar tool is then changed to to the "select annotation" tool which can then be used to selected the new annotation. Once selected the annotation properties pan is enabled and the annotation look and feel can be edited and as well as adding a new action.