brazilian portuguese translation added

brazilian portuguese translation added;

it may be necessary to rename it to pt-BR.yml depending on your sysconfig (perhaps on mac machines?). I run redmine in a linux box (mostly RHEL based), and plugins with "pt-BR.yml" files are ignored and translations get confused. I don't know if this is a specific linux + redmine 2.x behaviour or because I've been using the same redmine codebase since 0.X (something) and upgrading, upgrading, upgrading ... anyway, it's there :)

cheers