Allow foregrounding of applications

This feature has been sitting on the backburner for too long.  Now
you can foreground an application in three ways:

1)  At compile-time, use foreground => 1 in your constructor
2)  At run-time from the command itself: init.pl foreground
3)  At run-time from the environment settings: DC_FOREGROUND=1 init.pl start

This closes #15