Sudoku: 
- stop entries creating zero possibilities for a field
- notify on errors when solving
Merge remote-tracking branch 'origin/master'
Vigenère Breaker: The first opened editor window is always used as input

Fix provided by Albert Veli,
https://github.com/jcryptool/crypto/issues/72

Signed-off-by: Dominik Schadow <dominikschadow@googlemail.com>
Merge branch 'master' of https://github.com/jcryptool/crypto.git
Grille fixed #38
don't show rotation for decryption