
Merging seaice_growth codes -- part 2 -- actual changes.

- compute ICE2SNOW as SEAICE_rhoIce/SEAICE_rhoSnow (2.7576) rather
  than 1000.0 _d 0/SEAICE_rhoSnow*ICE2WATR (2.7879 in lab_sea)
>> This obviously changes all results significantly,
>> so all the relevant experiments results will be updated.
- rid of WATR2SNOW
- use convertPRECIP2HI/convertHI2PRECIP to go back and
  forth between precip m/s units and ice meters

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