Add support for pluggable auth to MySQL

[mehcode]

• CLIENT_PLUGIN_AUTH
• SECURE_CONNECTION
• mysql_native_password
• Authentication Switch Request / Response
• caching_sha2_password ( https://mariadb.com/kb/en/caching_sha2_password-authentication-plugin/ )
• sha256_password ( https://mariadb.com/kb/en/sha256_password-plugin/#rsa-encrypted-password )

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Currently, in v0.1.0 MySQL only works with "empty" passwords.

[mehcode]

This should be resolved on master from #18

[mehcode]

This is now released in v0.1.2