improve latex macro usage in TOP manual and namelist clean up

latex/TOP/main/bibliography.bib

@@ -720,3 +720,14 @@
   year          = {2001},
   publisher     = {Wiley Online Library}
 }
+
+@article{         tinto_GMD19,
+  author        = "Tint\'o Prims, O. and Acosta, M. C. and Moore, A. M. and Castrillo, M. and Serradell, K. and Cort\'es, A. and Doblas-Reyes, F. J.",
+  title         = "How to use mixed precision in ocean models: exploring a potential reduction of numerical precision in NEMO 4.0 and ROMS 3.6",
+  journal       = "Geoscientific Model Development",
+  volume        = "12",
+  year          = "2019",
+  author        = "7",
+  pages         = "3135--3148",
+  doi           = "10.5194/gmd-12-3135-2019"
+}

latex/TOP/namelists/namopt

+!-----------------------------------------------------------------------
+&namtrc_opt      !  light availability in the water column
+!-----------------------------------------------------------------------
+!                !  file name       ! frequency (hours) ! variable  ! time interp. !  clim  ! 'yearly'/ ! weights  ! rotation ! land/sea mask !
+!                !                  !  (if <0  months)  !   name    !   (logical)  !  (T/F) ! 'monthly' ! filename ! pairing  ! filename      !
+   sn_par        = 'par.orca'       ,     24            , 'fr_par'  ,  .true.      , .true. , 'yearly'  , ''       , ''       , ''
+   cn_dir        = './'        ! root directory for the location of the dynamical files
+   ln_varpar     =  .true.     ! Read PAR from file
+   parlux        =  0.43       ! Fraction of shortwave as PAR
+   light_loc     = 'center'    ! Light location in the water cell ('center', 'integral')
+/