Disconnecting from WindowServer without explicit calls to DestroyWindow
would leave nulled-out WeakPtr's in the AppletManager applet list.
This led to a null dereference when adding a new applet, since we were
assuming the list contained no nulled-out applets.
This patch fixes the issue by always unregistering applet windows from
the AppletManager in ~ClientConnection(). We also do an extra pass of
pruning any nulled-out WeakPtrs from the applet list when adding to it.
Fixes#1551.
Now it actually defaults to "a < b" comparison, instead of forcing you
to provide a trivial less-than comparator. Also you can pass in any
collection type that has .begin() and .end() and we'll sort it for you.
Move applet logic to the own class. Remove applet code from MenuManager.
With new AppletManager applet order is configurable via WindowManager.ini file.
