Add Closed Inverse flag

[antonkomarev]

Still thinking about naming of method which will remove closed flag: unclose() or open().

If open() will be chosen in future there will be Classic\Open flag which will have methods open() and close() to follow naming convention. These flags wouldn't been able to work together because methods open() and close() will be broken.

WIth unclose() such collisions are excluded but Classic\Active flag already have activate() & deactivate() methods.