Please support encoding option for mysql database.yml

[cmrd-senya]

For postgresql you have the following rule:

    encoding: utf8 # Optional, also accept 'charset' as key, if both are present 'encoding' is used (defaults to 'utf8')

At the same time, for mysql you don't support encoding, you only support charset: https://github.com/TalentBox/sequel-rails/blob/master/lib/sequel_rails/storage/abstract.rb#L66

At the same time, with ActiveRecord encoding option is supported for mysql, and when you copy a config file from an AR based app, this is a little difference which can break stuff.

Please support encoding config option for mysql as well as it works now for postgres.