Updates to the gpsclock.

Try to keep things to one build of the code, most/all of this can be done at run time.

 * Remove the GPSCLOCK cmake config option
 * Revert edcu.c and sdf_monitor.c.  These are not used anymore and should just be dropped (for another commit).
 * Removed dead symmetricom/gps code from standalone_edcu.cc.
 * Updated the gps logic used by standalone_edcu.cc (gps.hh) to use gpsclock instead of the system time if /dev/gpstime is not available.
 * Minor refactor of the controllerAppUser.c and controllerIopUser.c to reduce the number of ifdefs (for ease of reading)
 * Reworked local_dc.c to use gpsclock to use /dev/gpstime if available or gpsclock if it is not available.