Separate the reading of ww3_shel.inp

[JessicaMeixner-NOAA]

Is your feature request related to a problem? Please describe.
Create a separate routine to read ww3_shel.inp so that both ww3_shel program and the mesh based cap can use the same routine for reading the ww3_shel.inp file (and ww3_shel.nml).

Describe the solution you'd like
New subroutine to read ww3_shel.inp to reduce repeated code, which will help with code maintenance.

Describe alternatives you've considered
All initialization needs for ww3_shel.inp could be moved into a subroutine.

Additional context
This is part of merging #641 to the develop branch

[arunchawla-NOAA]

There is already a function to read ww_shel.inp data in wave_shel_inp.F90, is the request to use this function in ww3_shel.F90?

[JessicaMeixner-NOAA]

@arunchawla-NOAA yes, this way we don't have duplicative code and if code needs updated its done once for both places.

[MatthewMasarik-NOAA]

@arunchawla-NOAA, this has been my task. I've started it but was pulled to higher priority items. It will take a small dedicated chunk of time that I can move through the duplicative regions and refactor the duplicated code out.