Display "number of games detected" when loading a game from the archive

[herzbube]

When the user selects an entry on the Archive tab the app displays an overview section for each game detected in the SGF file. If there are many games in the file (e.g. test file gameinfo.sgf) the user does not know how many games there are in the file without scrolling all the way to the bottom to the last game overview section.

To provide more information about the file content more quickly, add a table cell to the "Load result" section that displays the number of games detected.