Do now show non input fields in the list of available variables for model files

wcs/workflows.py

@@ -30,6 +30,7 @@ from quixote.html import htmltext
 
 from wcs.roles import Role, logged_users_role, get_user_roles
 from wcs.formdata import Evolution
+from wcs.fields import SubtitleField, TitleField, CommentField, PageField
 
 if not __name__.startswith('wcs.') and not __name__ == "__main__":
     raise ImportError('Import of workflows module must be absolute (import wcs.workflows)')
@@ -48,6 +49,8 @@ def get_varnames(fields):
     '''
     varnames = []
     for field in fields:
+        if isinstance(field, (SubtitleField, TitleField, CommentField, PageField)):
+                continue
         # add it as f$n$
         label = field.label
         if field.varname: