Script API: Implemented Mouse.GetModeView method

This implements Mouse.GetModeView and also separates the Animate flag from a cursor's view number.

Old behaviour is preserved for old game files.

For new game files, a cursor will only be animated if its view is > 0 and the Animate flag was set in the editor. If the Animate flag is set, ChangeModeView to 0 or a non-0 value can still be used to toggle whether a cursor is animated.

I think this is the neatest way to complete the API (ChangeModeGraphic/GetModeGraphic, ChangeModeView/GetModeView). I'm happy to commit this again without the Animate requirement if anyone disagrees with it. I just think it would make the initial value of GetModeView a bit confusing for cursors where Animate = false. e.g. Questions like, why does it return 0 and not the number set in the editor?