Add sorting to classmap generator

This change adds an option to bin/classmap_generator.php to alphabetically sort the classmap list. This may seem unnecessary, but it has fixed several headaches for the group I work with.  Every time a developer runs the script to build the classmap files, it builds a list in a different order.  In many cases this would cause a conflict when an remote branch was merged locally.  Even though conflicts are still possible with sorting, they are more manageable.