* Life.csproj:
* GuiLabel.cs:
* GuiComponent.cs:
* IGuiStyleService.cs: 

* LifeGame.cs: Add the IGuiStyleService to services and initialized
  the default style.

* GuiStyle.cs: Use the IGuiStyleService.

* GuiStyleService.cs: Made GuiStyleService disposable to proper unload
  the contented style and implemented change of the style in game.