TFVC: Cannot undo file deletion

[ForNeVeR]

1. Delete any file (or directory) under TFVC
2. Press Ctrl-Z in IDE

Expected result: file should be undeleted with previous contents, VCS should show no changes
Actual result: user will be asked whether they want to Add the file; addition will never work; file will still be marked as deleted and rollback won't work properly.

[ForNeVeR]

We'll fix undo operation for deleted files, and disallow to undo deleted directories (since there's no easy way of doing that with the classic/legacy TFVC client).