creating a new group should check for the groups password strength

[KonstantinGasser]

When creating a new group the user needs to set a password to encrypt and decrypt the vault. As of now the password is not checked for its strength.

If the user adds a new group the password should be checked for its strength by using the security.PasswordStrength function altering if the password is insecure.

sherlock add group (not implemented but will be as laid out it #9) should therefore also have a --insecure flag to allow insecure passwords.

Furthermore the password check should also be implemented for setting up the default group when running sherlock setup