Change dither defaults to current Chandra ACIS

Starting in cycle 25, Chandra moved to a larger dither pattern for ACIS by default.
This changes the defaults in marx.par to match those ACIS patterns.
See: https://cxc.harvard.edu/proposer/POG/html/chap5.html#tb:dither

fixes #64

marx/par/marx.par

@@ -134,11 +134,11 @@ RA_Nom,r,a,250.2134679741175,,,"RA_NOM for dither (degrees)"
 Dec_Nom,r,a,-53.75743813458669,,,"DEC_NOM for dither (degrees)"
 Roll_Nom,r,a,237.36968458476,,,"ROLL_NOM for dither (degrees)"
 #
-DitherAmp_RA,r,a,8,0,,"Amplitude for RA dither (arcsec)"
-DitherAmp_Dec,r,a,8,0,,"Amplitude for Dec dither (arcsec)"
+DitherAmp_RA,r,a,16,0,,"Amplitude for RA dither (arcsec)"
+DitherAmp_Dec,r,a,16,0,,"Amplitude for Dec dither (arcsec)"
 DitherAmp_Roll,r,a,0,0,,"Amplitude for Roll dither (arcsec)"
-DitherPeriod_RA,r,a,1000,1,,"Period for RA dither (sec)"
-DitherPeriod_Dec,r,a,707,1,,"Period for Dec dither (sec)"
+DitherPeriod_RA,r,a,1414.2,1,,"Period for RA dither (sec)"
+DitherPeriod_Dec,r,a,2000,1,,"Period for Dec dither (sec)"
 DitherPeriod_Roll,r,a,1e5,1,,"Period for Roll dither (sec)"
 DitherPhase_RA,r,a,0,,,"Phase for RA dither (radians)"
 DitherPhase_Dec,r,a,0,,,"Phase for Dec dither (radians)"