Added ability to Tap & SendKeys from the Inspector

The Inspector for the Mac has interaction buttons, I have enabled some of the interaction buttons for this project, specifically Tap and SendKeys. 

This patch also contains an update to the Styles.xaml to correct an issue with all buttons being sized to 40x40 causing UI resizing issues.

I have also updated the INode and abstract to add new functionality to expose the ResourceId (Android) or Name (iOS) for the purposes of Tap and SendKeys.

I have moved ObservableCollection<UIAutomatorNodeVM> into a class NodeTree<T> where T is UIAutomatorNodeVM. This was done so if the collection type needs modifying it only needs doing once. Also, shared common function can be placed in static methods.

The INode interface was updated to expose Id.
Added function to return the Id of the element (which differs between Android and iPhone but has a roughtly common use?... )