fire init is setting the wrong config key for the theme name

[duncancm9]

See https://github.com/fourkitchens/fire/blob/3.x/src/Robo/Plugin/Commands/InitCommand.php#L84

But this function is looking for a local_fe_theme_name:

https://github.com/fourkitchens/fire/blob/3.x/src/Robo/Plugin/Commands/FireCommandBase.php#L55