Hand/Private window security & workflow improvement

Logged as bug# 13746 :

Normally a hand / private window is inaccessible to the non-owning side.

It can happen that a player starts a game by joining one side, opens a private window and then swaps to another side that does not own the private window. In this state, the player will be able to view the contents of the private window but not access the pieces in it (though the window’s toolbar buttons still work for that player).

In a solo game, the solo player may wish to switch between sides as an alternative to a true “Solitaire” role. One way for the module writer to support such a solo mode is to integrate side switching with opening up the active side’s hand window. However, without a means of determining the private window’s display state (hide/unhide), the method will depend on the user not to close/open hand windows manually.

Both these issues could be resolved by automatically closing private windows when a user switches to a side that does not own that private window. Alternatively, an Unhidden private window should respond to the “Hide/Unhide” hot-key regardless of PlayerSide.