fix migration from old to new encryption
make legacyDecrypt() private als always call legacyBlockDecrypt() from other classes
legacyBlockDecryprt() needs to be public
Merge branch 'master' into remove_unused_vars

Conflicts:
	apps/files_encryption/hooks/hooks.php
	apps/files_encryption/lib/crypt.php
	apps/files_encryption/lib/proxy.php