Editor Improvements

[BryonLewis]

resolves #18

• Cursor Handle changes. I.E when hovering over cursors for editing it indicates with the pointer style the action that it enables
• Add global cursor event for indicating that a new polygon is being created
• Fixed issues with editing and changing modes, specifically when deleting an annotation that was selected
• Update the width and frequency of an annotation in real time as the annotation is edited
• Current State for the Mode, 'creating', 'editing' is indicated in the top bar.
• Center the annotation when clicking on it in the list
• Add keyboard Up/Down to go through annotations
• Sort annotations by start time in the annotation list.
• Add scroll to annotation when selected.

AnnotationEditorImprovementsSmall.mp4