Default layout for all
SRootContainer derivates.
There might be situations when you want to use a custom SRootLayout. Why?
Because by setting an SFrame's layout you can change the look of a whole
application. Since only the object called "frame" will be replaced with
the content element, you can statically define XHTML elements such as a
border, a title or a footer line by defining your own template with a STemplateLayout.