BUG: Disable fiducials in light box mode.

Fiducials are not being properly positioned when in light box mode, this change disables them and gives the user a warning that they are being disabled (new fiducials can still be placed, but will not be visible until you exit light box mode). This change fixes bugs that were left from the attempt to use the point handle widgets in 2D so that they can be properly hidden: fix the visibility setting on the point handles in light box mode, disable the point handles when invisible so that they don't become visible when the mouse is near it, updated a visibility check comparision to match return type from method. Also removed warning messages by casting the 3d handles before changing the picking state. Fixed a bug wherein if you had a mix of fiducials having been placed in lightbox and not light box mode, the seed widget would have a mix of 2d and 3d handles. This fix removes all the current handles so that they're properly recreated as the necessary type.

Issue #1690