Sha256 names functionality

[williamzeni99]

Hi!
I worked on your code and I have just implemented a new functionality: now the user can choose to encrypt also the files names and related directories. To do that it adds a new json file called "metadata" where old names are stored. During the decryption it automatically searchs for the metadata file: if found, it restores the names, if not it decrypts without doing it.

If you want to encrypt a single file, the metadata file will be in the same directory of the file. Whereas, if you want to encrypt a directory, it stores the metadata file in the directory you want to encrypt.

The encryption is done by using crypto module, making the sha256 of the file/dir name with a random generated salt.
I found it more convinient than doing a "real encryption" of a string. Obviously the metadatafile is encrypted so the strength of the code is related of the robustness of the password (maybe I will implement a way to suggest real robust password according owasp guide lines)

I didn't add any log of this functionality yet.