Support `unix_socket` authentication and passwordless

[MathiasSven]

Feature Description: It would be easier for deployment if dynmap supported either logging in without a password, or using the unix_socket authentication method that is based on the user running the service (in this case minecraft most likely), though I think unix_socket is MariaDB only. For the former, I don't see a problem in not having a password for a local only account that has access to the Dynmap database only.

Additional Context: I tried to do both unix_socket authentication and a user with no password, and on both of these, even when I comment out the password in configuration.txt for the storage section, dynmap seems to still try to connect to the database using a password:

Access denied for user 'minecraft'@'localhost' (using password: YES)

So that is why I assume the only way to log into the database currently is using a password.