Externalize duplicate subroutines read_<type>_input(fileid,keyword,value,default)

[ahmad-el-sayed]

These are utilities that should be externalized to a dedicated module. Duplicates exist in modules sfincs_snapwave and sfincs_input.

Reason to move to a dedicated module:

• It is not the responsibility of sfincs_snapwave and sfincs_input modules to provide such functionality
• Easier maintenance

Note that somehow it is necessary to call notabs in module sfincs_input but it is not in sfincs_snapwave. If this is intended, such call can be controlled via an optional boolean parameter in the signature of read_<type>_input in the unified module.