make methods private which are not used from outside
adapt tests to the changes in crypt.php
remove todo item
fixing typos and PHPDoc
remove old comments, TODos, etc.
Merge branch 'encryption_clean_up' of github.com:owncloud/core into encryption_clean_up
change decryptUnknownKeyfile() to decryptKeyfile(), we always use openssl_seal
Merge pull request #4352 from owncloud/encryption_clean_up

crypt.php clean up