grepg [WP]: reorganize option list

options were listed in chronological order of implementation;
organize them instead in groups of similar topic

src/green/grepg/grepg.f

@@ -115,6 +115,7 @@ c     V2.41  03/11/11   resolved a fatal error when addressing the data array
 c                       for scaling gabor matrix values
 c     V2.42  06/02/17   support colored dispersion curve on white
 c                       background (implemented in grepg_dopicks.f)
+c     V2.43  11/12/19   reorganize usage information
 c
 c======================================================================
       program grepg
@@ -128,7 +129,7 @@ c
       character titleformat*130
 c  program version:
       character*79 version
-      parameter(version='GREPG V2.42  plot Fourier-Bessel coefficients')
+      parameter(version='GREPG V2.43  plot Fourier-Bessel coefficients')
 
 c  declare variables for io
       character*200 filename
@@ -235,25 +236,29 @@ c======================================================================
 c  give basic information
       print *,version
       print *,
-     &'Usage: grepg filename [-d dev] [-i] [-c] [-r L,dx] [-R|I] [-L]'
+     &'Usage: grepg filename [-v] [-P] [-D]'
       print *,'               ',
-     &'       [-q] [-p p] [-g] [-l width] [-s] [-P] [-S]'
+     &'       [-d dev] [-G file] [-F file] [-ff file]'
       print *,'               ',
-     &'       [-m lim] [-G file] [-H ch] [-F file] [-v]'
+     &'       [-R|I] [-L] [-p p] [-E]'
       print *,'               ',
-     &'       [-N c,w] [-T title] [-X label] [-Y label] [-W]'
+     &'       [-C] [-a a,g] [-Pr] [-O i,m,s]'
       print *,'               ',
-     &'       [-n value] [-A label] [-M lim] [-C] [-B label]'
+     &'       [-S] [-t n,m] [-Q] [-K o,t]'
       print *,'               ',
-     &'       [-O i,m,s] [-a a,g] [-f n] [-t n,m] [-Q] [-e lim]'
+     &'       [-s] [-st] [-f n] [-N c,w]'
       print *,'               ',
-     &'       [-K o,t] [-b width] [-x R,G,B] [-y R,G,B] [-h]'
+     &'       [-n value] [-M limit] [-e limit] [-m limit]'
       print *,'               ',
-     &'       [-Fc r,g,b,w] [-Ah h] [-t n,m] [-Ta anno]'
+     &'       [-q] [-g] [-l w] [-H ch] [-W] [-b w] [-c] [-Fc r,g,b,w]'
       print *,'               ',
-     &'       [-FC n] [-Fl n] [-Pr] [-Ww w]'
+     &'       [-T title] [-Ta anno] [-X label] [-Y label] [-A label]'
       print *,'               ',
-     &'       [-ff filename] [-st]'
+     &'       [-Ah h] [-B label] [-x r,g,b] [-y r,g,b] [-h] [-i]'
+      print *,'               ',
+     &'       [-FC n] [-Fl n] [-Ww w]'
+      print *,'               ',
+     &'       [-r L,dx]'
       print *,
      &'or:    grepg -help'
       call tf_seitosh_reference