Detect string variable types in the Python-Fortran dicts

[timothy-nunn]

Add variables of string type to the Python-Fortran dictionaries. This should avoid problems like

File "/home/oliver/development/PROCESS/process/io/in_dat.py", line 695, in parameter_type
    param_type = dicts["DICT_VAR_TYPE"][name]
                 ~~~~~~~~~~~~~~~~~~~~~~^^^^^^
KeyError: 'fwcoolant'

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 29.56%. Comparing base (7844aa2) to head (d1a3582).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3421   +/-   ##
=======================================
  Coverage   29.56%   29.56%           
=======================================
  Files          78       78           
  Lines       19131    19131           
=======================================
  Hits         5656     5656           
  Misses      13475    13475           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[timothy-nunn]

@clmould worth talking to @oliverfunk to check that this works