Update cctest/inc/ccref.h to reference pp function
Update libfg/src/pp.c to fix calculation of PP function duration
Rename libfg pp.c/h to ramp.c/h
Rename cctest/inc/func/pp.h to ramp.h to match change in libfg
Refactor libfg ramp.h to refer to ramp not pp
Refactor libfg ramp.c to refer to ramp not pp
Update libreg rst.c to fix calculation of t0_correction
Update to refactor PP function to RAMP