Set Culture directly

Instead of setting “language” and “format local”, let the user set the Culture string, like “en-US” or “pt-BR”.

Today, there is no way to set “pt-BR”, only “pt-pt”, and this is a problem when showing values, for example.

Let the culture be a free string, with a default value, like “en-US”, just to remember what to set there. The user who configs this plugin knows what it means and how to set the correct culture.