Script API: Implemented Mouse.GetModeView method

This implements Mouse.GetModeView. This rounds out the Mouse API for views and graphics (ChangeModeGraphic/GetModeGraphic, ChangeModeView/GetModeView). It also passes the value of the Animate flag through to the runtime mouse cursor. Essentially it decouples the Animate flag from the value of a cursor's view. Here's a summary of the changes. Note: Old behaviour is preserved for old game files.

Old:
 - ChangeModeView to > 0 could be used to make any cursor animated
 - ChangeModeView to 0 could be used to "turn off" an animated cursor
 - The view of an animated cursor would initially be the value set in the editor
 - The view of a non-animated cursor would initially be 0

New:
 - ChangeModeView to > 0 will animate a cursor if it has Animated = true set in the editor
 - ChangeModeView to 0 will "turn off" an animated cursor
 - The view of an animated cursor will initially be the value set in the editor
 - The view of a non-animated cursor will initially be the value set in the editor

I'm happy to commit this again without the Animate flag change if anyone disagrees with it. We could instead simplify the implementation and document that the initial view of an non-animated cursor is always 0.