Fixes #1069. Clean up WW3 Cmake

[mathomp4]

Closes #1069

This PR is an attempt to clean up the WW3 CMake code by preventing duplication. This update uses the switch_strings string and makes a W3_-prefixed list from that.

I'll keep draft until @adarmenov can test. At the moment, I can say things build, but maybe it's making garbage WW3 code since I can't run test. But the resulting CMake files have:

Fortran_DEFINES = -DESMA64 -DFORTRAN_COMPILER_SUPPORTS_ASSUMED_TYPE 
-DFORTRAN_COMPILER_SUPPORTS_FINDLOC -DH5_HAVE_PARALLEL -DHAS_NETCDF3 
-DHAS_NETCDF4 -DHAVE_SHMEM -DNETCDF_NEED_NF_MPIIO 
-DW3_BS0 -DW3_BT1 -DW3_CRT0 -DW3_CRX0 -DW3_DB1 -DW3_DIST 
-DW3_FLD2 -DW3_FLX0 -DW3_IC0 -DW3_IS0 -DW3_LN1 -DW3_MLIM 
-DW3_MPI -DW3_NL1 -DW3_NOGRB -DW3_O0 -DW3_O1 -DW3_O2 -DW3_O3 
-DW3_O4 -DW3_O5 -DW3_O6 -DW3_O7 -DW3_PR3 -DW3_REF0 -DW3_SCRIP 
-DW3_ST4 -DW3_STAB0 -DW3_TR0 -DW3_UQ -DW3_WNT0 -DW3_WNX0 -DW3_XX0 -DsysLinux

which seems right. (NOTE: I added the newlines in that. In Cmake land it's one looooong line)