Added metadata logic for sediment tracers boundaries

[arango]

Updated varindo.dat and mod_ncparam.F to include the metadata for cohesive and noncohesive input boundary variables. Recall the the logic for these variables are special because it depends on the number of sediment classes. I added the following comment to varinfo.dat for clarity:

!
!------------------------------------------------------------------------------
!  Sediment variables:  The actual variable name for some of the sediment
!                       tracers are set-up internally in "mod_ncparam.F".
!  It depends on the mumber of cohesive and noncohesive sediment tracers
!  for a particular application. For example if you have 1 cohesive and
!  2 noncohesive sediment classes, the variable names are:
!
!    "mud_"          becomes   "mud_01"
!    "mud_west_"     becomes   "mud_west_01"
!    "mud_east_"     becomes   "mud_east_01"
!    "mud_south_"    becomes   "mud_south_01"
!    "mud_north_"    becomes   "mud_north_01"
!
!    "sand_"         becomes   "sand_01",       "sand_02"
!    "sand_west"     becomes   "sand_west_01",  "sand_west_02"
!    "sand_east"     becomes   "sand_east_01",  "sand_east_02"
!    "sand_south"    becomes   "sand_south_01", "sand_south_02"
!    "sand_north"    becomes   "sand_north_01", "sand_north_02"
!------------------------------------------------------------------------------
!

Many thanks to Do-Seong Byun for ​bringing this to my attention.