Used by classes that need to retrieve a component by its complete id, or a page by its logical
page name or root component class. The complete id is the FQCN of the containing page, a colon,
and the nested component id. It may also just be the page name (for the root component of a
page).
Returns the page identified by its logical page name. A logical page name is the short form
of a page name often emebedded into URLs.
Parameters: pageName - the logical page name the corresponding page's root component throws: IllegalArgumentException - if the page can not be found