[WIDGPT-57] Updated support for handling window-state specific JSPs.  Up...

Update to my previous PR based on post-merge pull request comments.    Previously, I had added support for a new portlet preference for configuring the JSP page to use based on window state.   This version relys on convention and removes the portlet preference.

In this case, the portlet will first look for a JSP like [basename].[window-state].jsp where basename is the configured JSP name and window-state is the current window state (lowercase).   If that file exists, it will be used.   If it does not exist, the portlet will fall back to just using the configured JSP.

@jameswennmacher let me know if this is not more what you had in mind.
This looks like maybe it's trying to be Spring MVC's `ViewResolver` interface?