Localization support and Playfield improvements

Added localization support

var loc = new Localization(@"ScenarioFolder\Extras\Localization.csv");
var translated = loc.Localize(key: "HullFull", language: "English");

Assert.Equal("Steel Block", translated);

Added TryParseRootVariable to Playfield

This will easily allow reading root variables from various IPlayfieldFiles.

var playfield = new PlayField(playfieldFolder);
playfield.TryParseRootVariable("PlayfieldType", out PlayfieldType value);