update ScreenMiniMenuContext

The recent addition of an extra "Edit" optionrow had broken this, visually. This screen now accommodates a flexible number of optionrows should they change again in the future.
simplify ScreenMessage utility

I formerly had two distinct utility functions: SM() which was for strings, and SMPairs() which was for tables.  This effectively combines them so I can always use SM(), which is easier to type. :)