Update config_spec.md
Update docs for model_dir
@@ -259,6 +259,8 @@ to interpret this parameter as an absolute system path or a path relative to
the current command. It's defaulting to the directory of the current
configuration file if left blank.
+It is assumed that `model_dir` contains two folders, `models` and `logs`.
+
###### `dataset_split_file`
File assigning subjects to training/validation/inference subsets.
If the string is a relative path, NiftyNet interpret this as relative to `model_dir`.
