Reading in wave forcing files

[NoahDay]

Extend on wave_spec_data (ice_forcing.F90) to enable the reading in of WW3 output files.

[NoahDay]

I've commented out the following line
if (use_leap_years) days_per_year = 366 !overrides setting of 365 in ice_calendar
since I think this means that if leap years are allowed in the simulation then every year is a leap year.

[NoahDay]

Files are read in 4 times per day (6-hourly). This means that for a full year of data the files are approximately 20GB in size.