group: Fixes for 3-analysis-levels
group: Fixes for 3-analysis-levels

- Fix referencing "session_list" rather than "sessions".
- Fixes to N=1 group-level analysis processing following testing.
- Fix generating list of b-values prior to using the list of class members to check for requisite input files.
- Create output "connectome" sub-directory.

BIDS-Apps/MRtrix3_connectome