Added cursor guidelines for annotating

[clayshieh]

guidelines will show and update whenever not operating with an annotation object

[antingshen]

Should hide guide lines when drawing a box. Maybe consider hiding mouse cursor when guide lines are present

[clayshieh]

Fixed.

[clayshieh]

Also fixed for hiding mouse cursor when guide lines are present

[antingshen]

I had the tester test this today, he really likes the lines. But there's a couple of small problems:

• The lines still lag a little bit compared to mouse... not sure how we can fix this
• It's more difficult to grab edges/corners of existing boxes for some reason
• Cursor is still hidden when outside the frame of the video