Dedicated segmentation path option, minor bug fixes, updated simnibs call

[jkosciessa]

These updates add the option to specify parameters.seg_path as the location where simnibs' m2m folders will be deposited. I added this path directly to the main script, so did not yet test it out wiht yaml specification. If no seg_path is provided, data_path is used as a default, ensuring backward compatibility.

There are a few other changes:

• Whenever I stumbled upon path composition via sprintf(path/xxx), I changed it to fullfile(path, sprintf).
• The simnibs charm command when invoked will now force qform and force run, overwriting eventual files. The command is only invoked after overwriting is confirmed in the context of the script, but still something to be aware of.
• minor bug fixes

[achetverikov]

Your last commit seem to be a add hotfix for mni2subjects function, which is already in the code, but for some reason there are conflicts related to previous commits. Could be because I tried to rewrite the emails for @eleonoracarpino in the history. I can merge them, but it would be better I think if you add the commits you mention in your description ('seg_path') so we can see how it matches with other changes I've made and merge everything.

As an additional note, I've made forceqform optional in my code, wouldn't want to force it on the user.

[jkosciessa]

@achetverikov Dumb me, I didn't yet push the changes. The relevant commits are f5873ffa7a76fef05b1f879aa0889346e824ca9e for most of the changes described above, and f4a6c433d7fdd5a39eb922bd48da5a8b3ac5709d for a small bug fix. Let me know if I need to open a new pull request after pushing these commits.

Optional forceqform is of course a better option.

[achetverikov]

Merged! I also moved the checks for parameter.seg_path to load_parameters(). And restored use_donders_hpc flag check in run_segmentation. Was there a particular reason you removed it?